Replacing the cylindrical lock insert is one of the most common locksmith tasks. Whether you have just moved in, lost your key, or simply want to increase the security of your flat, a correctly chosen insert is essential. This guide will show you what to look for and how to navigate the available options.
Why replace a cylindrical liner?
There are several reasons for replacing the filter, and each is relevant:
- Moving house - you do not know how many key copies the previous owner or tenant distributed. In such cases, replacing the lock cylinder is an absolute security necessity.
- Lost key - A found key in the wrong hands is a direct threat. It does not matter whether the key was lost on public transport or forgotten by an employee of a supplier company.
- Safety upgrade - Old inserts without security certification can be opened by an experienced intruder in a few seconds. A modern certified insert resists significantly longer and substantially reduces the risk of burglary.
- Wear and tear - Does the lock squeak, does the key stick or is it difficult to lock properly? The cylinder is worn and needs replacing.
- Employee departure or distribution - Anyone who had access to your key and has since left is a potential risk.
Safety classes of inserts (SC 1-5)
Cylindrical inserts in the Czech Republic are classified into security classes according to standard ČSN EN 1303. The higher the number, the better the insert resists a break-in attempt.
BT 1 (basic) - Minimum resistance. Typical of older apartment doors, garages or cellars. Suitable only where there is no valuables.
BT 2 (standard) - Basic durability for apartment buildings. The most common class installed in new flats.
BT 3 (safety) - Resistant to drilling, prying and opening with special tools. Recommended for detached houses and flats containing valuable items.
BT 4 (high security) - Certification for inserts resistant even to destructive attacks. Suitable for companies, warehouses and archives.
BT 5 (maximum safety) - Highest durability, designed for banks, vault rooms and critical workstations.
For an apartment in Prague we recommend at least BT 3. For a surcharge compared to BT 2, you receive significantly higher protection: an investment that pays off.
Top manufacturers of cylindrical inserts
You will find dozens of brands on the market, but in practice only a handful of manufacturers have proven themselves:
- FAB - Czech classic, affordable price, good service network. FAB 3*** is a popular combination of price and safety for flats.
- Tokoz - another Czech manufacturer with a long tradition. The R4 series offers solid security at a reasonable price.
- Mul-T-Lock - Israeli manufacturer, a recognised brand for higher security classes. The patented key system makes copying keys difficult.
- EVVA - Austrian manufacturer, top-tier quality. EVVA EPS or MCS inserts are practically uncopyable and withstand even sophisticated attacks. Higher price, but justified by premium workmanship.
- ABUS - German reliability, good selection across various price ranges.
How to determine the correct filter size?
The cylindrical insert must fit the door precisely: an insert that is too short or too long will either not install or be unsafe. Measuring is straightforward:
- Remove the existing insert (unscrew the central screw and pull out the insert with a key).
- Measure the distance from the centre (centre of the rotating cylinder) to the outer edge. This is the outer part (e.g. 35 mm).
- Measure the length from the centre to the inner edge. This is the internal part (e.g. 35 mm).
- Record the result as 35/35 - this is the filter size you are looking for.
Warning: The inner side (the one inside the flat) is usually 5-10 mm longer because the hardware is more substantial. The most common dimensions for flat inserts are 30/35, 35/35 or 30/40 mm. If you are unsure, take the old insert with you to the shop or call us - we will measure it on site.
When to call a handyman versus doing it yourself?
Replacing the cylindrical cartridge is theoretically a DIY job. You just need a screwdriver and the correct cartridge. In practice, however, a number of complications arise:
- The insert is blocked or damaged and cannot be removed.
- The doors have non-standard fittings or a multi-point lock.
- You don't know how to measure the length correctly and don't want to risk a wrong purchase.
- Do you want to be sure that the insert is correctly installed and safe?
A professional lock cylinder replacement by a locksmith usually takes 15-30 minutes. We bring a selection of cylinders in various security classes, so you do not need to search for or purchase anything in advance.
🔐 Do you need to replace a cartridge?
We will arrive within 30 minutes, select a suitable insert and install it. The price is stated in advance.
📞 +420 277 278 911 Call Zámečník Centrum in PragueSummary: key points to remember
- When moving, always replace the lock cylinder. You never know how many keys are in circulation.
- For an apartment in Prague, choose at least BT 3.
- Manufacturer verification: FAB, Tokoz, Mul-T-Lock, EVVA, ABUS.
- Measure the insert length from the centre to both ends: record as, for example, 35/35 mm.
- If you are unsure about anything, give us a call. We will be happy to advise you without any obligation.
Are you interested in replacing a filter or do you just need advice? Take a look at our page on replacing a cylindrical liner or call us directly on 277 278 911.
We provide services throughout Prague. We guarantee the fastest arrival for Prague 1 and surrounding areas.
Also read: Locked myself out: what to do step by step →