Euro lock cylinder sizes read as two numbers — 30/30, 35/35, 40/40 — measured in mm from the centre of the fixing screw to each end of the barrel. A 40/40 totals 80 mm. Get the size right first, then judge security: that order prevents almost every costly mistake in this category.

The euro profile cylinder is the most widely used lock format in Europe, and it has spread well beyond it — into aluminium storefronts, apartment blocks, multipoint composite doors and, increasingly, North American condominium and commercial projects. Its appeal is modular: you can swap the cylinder in minutes without replacing the mortise lockcase, which makes upgrading security cheap and fast .

How to measure correctly

Remove the cylinder before you measure. Open the door, undo the retaining screw on the door edge, insert the key, turn it about an eighth of a turn to align the cam, and slide the barrel out. Then measure from the centre of the fixing screw hole​ to each end, in millimetres, and record both sides .

Common splits and their overall lengths:

Two cylinders can share the same total and still be wrong: 30/50 and 40/40 both total 80 mm but are not interchangeable. Always round up to the next 5 mm increment, exclude the thumbturn from the body measurement, and note which side faces outside .

Fit matters for security, not just looks. A cylinder that protrudes too far past the escutcheon gives an attacker something to grip and break .

Types

• Double cylinder​ — key operation from both sides.
• Thumbturn cylinder​ — key outside, turn inside; popular for fast exit and for homes where a key left inside could trap occupants.
• Half (single) cylinder​ — one working side only, for garages, shutters and cupboards.
• Toilet/privacy cylinder​ — thumbturn one side, emergency release slot on the other.
• Oval and rim cylinders​ — regional variants that still follow the same modular logic.

Body section is standardised at roughly Ø17 × 33 × 10 mm, with a cam such as R15 × 6.5, and lengths are typically produced in 5 mm increments .

Standards that actually mean something

EN 1303​ is the classification standard. Its code reads across durability, key-related security, attack resistance, corrosion and more — for example a 6-pin brass cylinder can reach Grade 4 or better in key-related security and 100,000 test cycles . DIN 18252​ covers the profile and cam geometry, so a compliant cylinder drops into any EN-standard lockcase. EN 1634-1​ covers fire-door suitability, which matters for commercial and public buildings .

For attack resistance, UK and insurer-recognised marks are the practical reference: TS007 1-star​ cylinders are kitemarked with anti-drill, anti-pick and anti-bump performance, while 3-star​ cylinders add full anti-snap and need no special handle. Note there is no 2-star cylinder — 2-star belongs to security handles, and a 1-star cylinder behind a 2-star handle reaches 3-star equivalent . Sold Secure SS312 Diamond​ is the independent top-tier equivalent .

Security features to ask for by name

• Anti-snap​ — a sacrificial snap line breaks away under force while the protected mechanism keeps the door locked.
• Anti-pick​ — shaped or telescopic pins resist manipulation.
• Anti-bump​ — pin geometry that will not jump under a bump key.
• Anti-drill​ — hardened steel pins and plates in the plug and body.
• Anti-plug pull / anti-twist​ — reinforced circlips and multi-part bodies.
• Key control​ — patented or dimple keyways and security cards that block unauthorised duplication .

Also confirm the supply package: number of keys, master keying or keyed-alike options, finish choices, and the warranty.

Materials, smart upgrades and sourcing

Solid brass (commonly HPB59-1) remains the benchmark body material for corrosion resistance and smooth operation, with satin chrome, brass, black and custom finishes available. Mechanical cylinders increasingly sit alongside smart electronic cylinders​ — retrofittable, battery-powered barrels that fit the same euro profile without wiring or drilling .

If you are sourcing at volume, work with a manufacturer rather than a trader. Zhongshan Goodtop Hardware Co., Ltd​ is a professional manufacturer of mechanical locks, smart locks, lock cylinders and other lock accessories in China — a one-stop source for cylinder bodies, cams, keys and matching furniture.

Frequently asked questions

Is 35/35 the most common size?​ 35/35 and 40/40 are both common; measure your own door rather than assuming.

Can I fit a 3-star cylinder myself?​ Usually yes — one screw, a key turn and a slide. Test the lock with the door open before closing it.

Does anti-snap matter if I have a security handle?​ A 1-star cylinder plus a 2-star rated handle reaches the same 3-star equivalent, so choose the combination that suits your door and budget .

Measure twice, check the standard, verify the certification applies to your exact model — and your euro lock cylinder will do its job quietly for a decade.