What size euro cylinder do I need?

Measure from the middle of the current lock to find out the required sizes: eg. Internal Length (A) 40mm / External Length (B) 50mm, the internal size is always stated first in the product description. 

Euro profile cylinder locks are a convenient way to change your keys without having to replace the entire lock and can be fitted in minutes without the need for any special tools or equipment.  It is the quickest and easiest way to upgrade the security rating of your property.