Every cylinder on a shop shelf calls itself high security. The gradings underneath that claim are what separate a lock that resists a real attack from one that resists a photograph of an attack.
ANSI Grade 1, 2 and 3
Grade 3 is residential-minimum and survives 800,000 cycles. Grade 2 is light commercial. Grade 1 is the commercial standard: a million cycles, ten strikes at 75 foot-pounds, and it is what we fit as standard on any door that has already been forced once.
The three-star question
Snapping is a euro-cylinder-specific attack, so the star rating that covers it matters more on a uPVC door than the ANSI grade does. Three stars on the cylinder, or one star plus a two-star handle, is the combination that holds. Anything less and the grade on the box is describing a different failure mode than the one that will actually be used.
