The Interlock Mercury X6 and Kaadas K9-5W are both push-pull digital door locks with fingerprint recognition, PIN access, RFID card access, mechanical key backup and built-in Wi-Fi.

But once we go beyond those core functions, the two locks are quite different.

The Kaadas K9-5W is built around the more traditional fingerprint digital-lock experience.

Our Mercury X6 adds 3D facial recognition, palm vein recognition, a built-in camera, indoor display and smart visitor functions on top of the usual fingerprint, PIN, card and key access.

So instead of simply saying one lock is better than the other, let's compare them feature by feature.

Mercury X6 vs Kaadas K9-5W at a Glance

Feature	Interlock Mercury X6	Kaadas K9-5W
Fingerprint	✅ Up to 100	✅ Up to 100
3D Facial Recognition	✅ Up to 50 faces	❌
Palm Vein Recognition	✅ Up to 50 palms	❌
RFID Card	✅ Up to 100 cards	✅ Up to 100 cards
PIN Code	✅	✅
Temporary PIN	✅	✅
Periodic PIN	✅	—
Mechanical Key	✅	✅
Built-in Wi-Fi	✅ No bridge required	✅ No bridge required
App Access Records	✅	✅
Built-in Camera	✅	❌
Indoor Display	✅	❌
Two-Way Audio Intercom	✅	❌
Remote Visitor Viewing	✅	❌
Built-in Doorbell	✅	❌
Door & Gate Synchronisation	✅ With compatible Mercury gate locks	✅ With compatible Kaadas gate locks
Battery	Rechargeable lithium battery	Replaceable batteries
Emergency Power	USB-C	Micro USB
Warranty	1-year onsite, product & rechargeable battery warranty	2-year onsite warranty
Usual Price	$899	$839

The K9-5W supports fingerprint, PIN, RFID card and mechanical key access, together with integrated Wi-Fi, temporary PIN creation and activity tracking through its app. Kaadas specifies storage for up to 100 fingerprints and 100 RFID cards.

Our Mercury X6 covers those core access methods while adding facial recognition, palm vein recognition and video-related functions.

1. Fingerprint Recognition

Both locks support fingerprint unlocking, and both can store up to 100 fingerprints.

The Kaadas K9-5W uses a Sweden FPC fingerprint sensor built into its push-pull handle.

The Mercury X6 also places the fingerprint sensor naturally around the handle area, so you can authenticate as you grip the lock.

If your household mainly wants fingerprint access, both locks already fulfil that requirement well.

The bigger difference is what happens when you want alternatives to fingerprint.

2. Facial Recognition

The Mercury X6 supports 3D facial recognition and can register up to 50 faces.

The K9-5W does not have facial recognition.

This gives X6 users another completely hands-free way to enter the home. Instead of touching the fingerprint sensor or keypad, a registered user can simply approach the lock and authenticate using their face.

It is also useful in a household where different family members prefer different access methods.

One person may use fingerprint every day, while another may prefer facial recognition.

3. Palm Vein Recognition

The Mercury X6 also supports palm vein recognition, with storage for up to 50 registered palms.

The K9-5W does not offer palm vein recognition.

Palm vein gives the X6 another contactless biometric access method. Users present their palm to the lock instead of placing their finger onto a sensor.

Combined with facial recognition and fingerprint recognition, this means our X6 gives homeowners three different biometric ways to unlock the same door:

Face, palm vein and fingerprint.

That is one of the biggest functional differences between these two locks.

4. PIN, RFID Card and Mechanical Key

For the conventional access methods, both locks are well equipped.

Both provide:

• PIN code access

• RFID card access

• Mechanical key backup

The K9-5W can register up to 100 RFID cards, while the X6 can similarly register up to 100 cards. Kaadas also provides mechanical key access as an emergency backup.

So if these are the functions you primarily care about, there isn't a major difference here.

5. Temporary Access

Both locks provide ways to give visitors temporary access without sharing your normal household PIN.

The K9-5W's app allows homeowners to generate temporary PINs and check lock activity.

Our Mercury X6 supports both one-time PINs and periodic PINs.

A one-time PIN is useful when someone only needs to enter once.

A periodic PIN is useful when someone should have access repeatedly during a particular period.

For example, instead of giving someone your permanent family PIN, you can create access specifically for the period when they need it.

6. Built-In Wi-Fi

Both locks have Wi-Fi built directly into the lock.

There is no separate Wi-Fi bridge required for either model.

Kaadas specifically integrates Wi-Fi into the K9-5W for functions such as temporary PIN creation, activity records and notifications.

The Mercury X6 similarly connects directly to Wi-Fi and uses the Tuya app for its connected functions.

So if the question is simply:

“Do I need to purchase another Wi-Fi bridge?”

The answer for both locks is no.

7. Camera and Indoor Viewer

This is where the two locks start serving quite different purposes.

The K9-5W is primarily an access-control digital lock.

Our Mercury X6 also includes a built-in camera and indoor IPS display.

When someone is outside the door, the homeowner can view the visitor directly from the indoor screen instead of needing a separate door viewer.

This means the X6 combines several devices into one:

Digital lock + biometric access + digital door viewer + smart visitor functions.

If you already have a separate door viewer or simply do not need one, this difference may not be important to you.

But if you want these functions integrated into your lock, the X6 provides them without requiring another device on the door.

8. Video Intercom: An Important Distinction

Our Mercury X6 also allows homeowners to communicate with visitors remotely through the mobile app.

There is an important distinction here:

Audio communication is two-way, while video viewing is one-way.

The homeowner can see the visitor through the lock's camera and both sides can communicate by audio.

However, the visitor does not see a video feed of the homeowner.

We prefer this arrangement from a privacy and safety perspective: you can identify and communicate with whoever is outside without needing to reveal yourself visually.

The K9-5W does not have an integrated camera or video intercom function.

9. Push-Pull Design

Both models use a push-pull form factor, but the physical designs are different.

The Kaadas K9-5W uses Kaadas' familiar straight push-pull handle design, with the fingerprint scanner integrated into the handle.

For our Mercury X6, we designed the body around a pronounced curved profile.

The curvature gives the hand a natural area to grip when pushing or pulling the door, while also giving the lock a more distinctive appearance.

There isn't really a universal winner here.

Design is personal.

Some homeowners may prefer the more conventional K9-5W shape, while others may prefer the curved profile of the X6.

What matters more is whether the lock fits your door properly and whether you like how it feels in daily use.

10. Door and Gate Synchronisation

Both locks can be part of synchronised door-and-gate setups.

The K9-5W supports dual unlocking when paired with compatible Kaadas gate-lock systems.

Our Mercury X6 can similarly be paired with compatible Mercury gate locks through the Advanced Module™ Synchronisation System.

For Singapore HDB homeowners, this can be more important than comparing the door locks individually.

If you intend to install both a digital door lock and digital gate lock, we recommend comparing the complete system:

• Which gate lock will be paired with it?

• How does the synchronisation work?

• What access methods are available on both locks?

• What happens if one lock or battery is unavailable?

• How easy is the complete setup to use every day?

The overall door-and-gate experience matters more than any single specification.

11. Battery System

The two locks use different approaches to power.

Our Mercury X6 uses a rechargeable lithium battery pack.

Instead of regularly replacing disposable batteries, you remove the battery pack, recharge it and reinstall it.

The X6 also has a USB-C emergency power port in case the main battery becomes depleted.

The K9-5W uses replaceable batteries and has a Micro USB emergency power port.

Neither system is automatically better.

Some homeowners prefer the simplicity of replacing batteries.

Others prefer having a rechargeable battery pack that can be charged and reused.

It comes down to which maintenance routine suits you better.

12. Warranty

Warranty is one area where the K9-5W has the longer coverage period.

Kaadas provides a 2-year onsite warranty for the K9-5W.

For our Mercury X6, we provide 1-year onsite warranty support, together with the product warranty and rechargeable battery warranty.

So if warranty duration alone is your deciding factor, the K9-5W gives you the longer standard warranty period.

If you are comparing the locks as a whole, however, warranty is one factor alongside the hardware, access methods, smart functions, installation and after-sales support.

13. Price: $899 vs $839

For a fair comparison, we prefer looking at the usual prices rather than temporary promotional prices.

The usual price of the Mercury X6 is:

$899

The usual price of the Kaadas K9-5W is:

$839

That is a difference of $60. Current promotional prices can change over time.

For that additional $60 at usual pricing, the main features added by the Mercury X6 are:

• 3D facial recognition

• Palm vein recognition

• Built-in camera

• Indoor display

• Remote visitor viewing

• Two-way audio communication

• Built-in doorbell

• Rechargeable lithium battery system

• One-time and periodic PIN options

That is probably the most useful way to look at the price difference.

It is not simply $899 lock vs $839 lock.

It is whether those additional functions are worth the $60 difference for your household.

So, Mercury X6 or Kaadas K9-5W?

If you mainly want a dependable fingerprint digital lock with PIN, card, mechanical key and Wi-Fi connectivity, the Kaadas K9-5W covers the fundamentals well.

It also comes with a longer 2-year onsite warranty.

If you don't need facial recognition, palm vein recognition, a camera or an indoor viewer, you may not need the additional functions of the X6.

The Mercury X6 makes more sense if you want a more complete smart-lock system, especially for a household where different people may prefer different ways of unlocking the door.

You get:

Fingerprint + 3D face + palm vein + PIN + card + key + app access

together with:

camera + indoor viewer + visitor communication + built-in Wi-Fi

in the same lock.

And at usual pricing, the difference between the two is $60.

That is ultimately why we see the Mercury X6 differently from a conventional fingerprint Wi-Fi lock.

It isn't necessarily about needing every feature every day.

It is about having more ways to enter, more ways to manage access, and more information about who is outside your door — all within one device.

Our Take

The Kaadas K9-5W is a good choice if you want a simpler, established fingerprint Wi-Fi lock and value the longer warranty period.

The Mercury X6 is the stronger choice if you're comparing functionality for the price.

For an additional $60 based on usual pricing, our X6 adds two additional biometric technologies — 3D facial recognition and palm vein recognition — together with an integrated camera, indoor viewer and visitor communication functions.

That's not us saying every homeowner needs those features.

But if you are comparing both locks feature-for-feature at a similar price point, the Mercury X6 simply gives you more ways to use the lock and more functions built into the same device.