Why there are Amazon links here: Brave Review is paid a commission for qualifying Amazon purchases made through the links below. Your price does not change, and using our links is entirely optional. How this works
Best Spare Cylinder for a Smart Lock for Fast, Hassle-Free Upgrades
A spare cylinder is the small part that decides whether a smart lock retrofit actually fits the door. This guide covers five options for three buyer types: the homeowner retrofitting an existing Euro-profile door, the tinkerer building a keyless setup from scratch, and the Kwikset owner who just wants a fresh key cut. Each pick below earns its place for a different reason, so the overview table is the fastest way to spot the right one before reading the full reviews.
Overview of the Picks
| Product | Key Spec | Best Use | Price Tier |
|---|---|---|---|
| Smart Door Lock, Euro Door Smart Cylinder Lock (Silver) | Euro-profile electronic cylinder | Full smart lock in one cylinder | Mid |
| Kwikset 83373 SmartKey Deadbolt Cylinder (Silver) | SmartKey deadbolt cylinder | Replacing a worn Kwikset cylinder | Budget |
| Yale Linus HS-K Cylinder (35 mm x 40 mm) | Sized for Yale Linus lock | Yale Linus owners needing a spare | Premium |
| Smart Lock DIY Keyless Double Replacement Cylinder (Silver, 90 mm) | TT Lock app, WiFi, 90 mm | DIY keyless builds on a Euro door | Premium |
| Kwikset SmartKey Re-Key Kit | DIY rekey tool set | Resetting keys without a new cylinder | Budget |
1. Smart Door Lock, Euro Door Smart Cylinder Lock (Silver)
Type: Euro-profile electronic cylinder
Function: Smart lock and cylinder in one unit
Finish: Silver
Door suitability: Wooden and iron security doors
Power source: Battery-powered electronic cylinder
This is the all-in-one route: instead of adding a motorized module to an existing cylinder, the whole electronic cylinder is the smart lock. It slots into a standard Euro-profile opening, so a wooden or iron security door that already takes that cylinder shape can be upgraded without a separate deadbolt assembly. The silver finish keeps it visually close to ordinary hardware, which matters on a front door where a bulky gadget would stand out. For a first smart lock on a Euro-profile door, this is the simplest path from key to app.
It suits renters and homeowners who want one purchase to cover both the cylinder and the electronics, and who are comfortable with app-based access. The caution is that a Euro-profile cylinder is only as good as the door’s existing cutout — a door drilled for a different profile will need adaptation, and the electronic internals mean this is not the part to buy if a purely mechanical spare is the goal.
Trade-off: Buying the electronics and the cylinder together means less flexibility if only one of the two ever fails.
2. Kwikset 83373 SmartKey Deadbolt Cylinder (Silver)
Type: Deadbolt cylinder
Keying: SmartKey re-key capable
Finish: Silver
Brand system: Kwikset
Intended use: Deadbolt replacement
Kwikset 83373 – Silver Smartkey Deadbolt Cylinder in Silver
The cheapest way to put a fresh cylinder in a Kwikset deadbolt. It is a straight replacement part for a worn or damaged cylinder, and because it is SmartKey-compatible it can be matched to an existing key rather than forcing a new one on the household. The silver finish matches standard Kwikset hardware, and the deadbolt format is the most common residential setup in the US. For anyone already inside the Kwikset ecosystem, this is the no-drama spare.
It suits the Kwikset owner replacing a single failed cylinder, or someone who wants a second cylinder keyed alike. The limit is compatibility: this is a Kwikset deadbolt part, so it will not fit a Euro-profile door, a Yale Linus, or a TT Lock system, and buyers outside the Kwikset world should look elsewhere.
Trade-off: Excellent value, but it only serves doors already cut for a Kwikset deadbolt.
3. Yale Linus HS-K Cylinder for Linus Smart Lock (35 mm x 40 mm)
Type: Replacement cylinder
Sizing: 35 mm x 40 mm
Compatibility: Yale Linus smart lock
Finish: Not stated beyond the model
Intended use: Spare or replacement for Linus
Yale Linus® HS-K Cylinder for Linus® Smart Lock – 35 mm x 40 mm
This is the OEM spare for the Yale Linus, and the dimensions in the name are the whole point. A Linus retrofit wraps around an existing cylinder, so the cylinder has to match the lock’s stated 35 mm by 40 mm sizing or the module will not seat correctly. Buying the official part removes the guesswork that comes with a generic cylinder, and it keeps the door’s mechanical key working alongside the app. For a Linus owner, this is the safe replacement.
It suits existing Linus users who need a spare or a replacement after a move, and anyone who values a guaranteed fit over saving a few dollars. The caution is the price and the narrow scope: this cylinder is for the Linus system specifically, so it is a poor choice for any other smart lock brand or for a door that has never had a Linus fitted.
Trade-off: A precise, official fit that costs more and helps no one outside the Yale Linus ecosystem.
4. Smart Lock DIY Keyless Double Replacement Cylinder (Silver, 90 mm)
Type: Euro-profile cylinder
Length: 90 mm
Connectivity: TT Lock app, WiFi
Function: Keyless double cylinder
Finish: Silver
The most configurable pick here. It is a 90 mm Euro cylinder with the electronics built in, managed through the TT Lock app and WiFi rather than a proprietary hub. That open app platform is the draw for DIYers who want keyless entry, remote access and the ability to add users without buying into a closed system. The double-cylinder format means it works from both sides of the door, which suits a front door where exit control matters.
It suits the hands-on buyer building a keyless Euro door on a budget who is happy to set up an app and troubleshoot pairing. The caution is the 90 mm length: Euro cylinders come in many lengths, and a door that needs a shorter or longer body will not accept this one, so the existing cylinder should be measured before ordering. App-dependent access also means a dead phone battery is a real consideration.
Trade-off: Flexible and app-driven, but the fixed 90 mm length rules out doors that need a different cylinder size.
5. Kwikset SmartKey Re-Key Kit
Type: DIY rekey tool set
Compatibility: Kwikset SmartKey locks only
Function: Key reset without a new cylinder
Intended use: Rekeying existing hardware
Not a cylinder at all, but the cheapest way to solve the problem a spare cylinder usually solves. The kit resets the keying on an existing Kwikset SmartKey lock, so a household can move to a new key without buying and fitting a replacement cylinder. It is a small tool set aimed at a five-minute job, and it keeps the original hardware in place. For a Kwikset owner whose only complaint is the key, this beats a new part.
It suits the Kwikset SmartKey owner who wants a fresh key after a move, a lost key or a tenant change, and who is comfortable following a short rekey procedure. The caution is in the name: it works only with Kwikset SmartKey locks and does nothing for non-SmartKey hardware or any other brand, so it is the wrong purchase for a Euro cylinder or a Yale system.
Trade-off: The lowest-cost fix of the five, but only if the lock is already a Kwikset SmartKey.
Before You Buy
- Cylinder profile: Euro-profile, deadbolt and retrofit cylinders are not interchangeable — match the shape of the existing hardware first.
- Length and sizing: Euro cylinders come in set lengths such as 90 mm, and retrofit parts like the Yale Linus cylinder are sized to the lock, so measure before ordering.
- Brand compatibility: Kwikset parts fit Kwikset, the Linus cylinder fits the Linus, and TT Lock hardware runs on its own app — cross-brand fitting is the most common mistake.
- Electronic vs mechanical: A powered cylinder needs battery planning and app setup; a plain replacement cylinder does not.
- Included accessories: Rekey kits and cylinders ship with different hardware, so check that keys or tools are in the box.
- Care: Keep a mechanical key accessible even on an electronic cylinder, and store the rekey tool somewhere findable.
Frequently Asked Questions
-
What is a spare cylinder for a smart lock actually for?
It replaces or supplements the mechanical cylinder the smart lock is built around, either to restore a worn part, match a new key, or add electronics to an existing Euro door. -
Can any cylinder be used with any smart lock?
No. Profile, length and brand all have to match — a Kwikset deadbolt cylinder will not fit a Euro-profile door, and the Yale Linus cylinder only suits the Linus. -
Is a rekey kit a substitute for a spare cylinder?
Only on Kwikset SmartKey locks. It changes the key on existing hardware rather than replacing the cylinder, and it does nothing for other brands. -
Do electronic cylinders need WiFi?
Some do, like the TT Lock model, while others work over Bluetooth or a local app. The listing for each product states its connectivity. -
How do I know which length to order?
Measure the existing cylinder from end to end, and match the size stated in the product name, such as the 90 mm TT Lock cylinder or the 35 mm x 40 mm Linus part. -
Can a spare cylinder be fitted without a locksmith?
Most of these are DIY parts, and the rekey kit is designed for home use, but a cylinder that does not seat cleanly should be checked by a professional.
Bottom Line
For most buyers, the Smart Door Lock Euro Cylinder is the best spare cylinder for a smart lock because it covers the cylinder and the electronics in a single purchase. Kwikset owners should take the cheaper 83373 replacement, Linus users should stay with the official Yale part, DIY builders get the most flexibility from the TT Lock cylinder, and anyone who just wants a new key can reach for the rekey kit.
