Rollerbolt operated by key or release lever from either side using a double cylinder (not supplied) or by key one side and release lever either side using a single cylinder (not supplied). Pierced to accept 20mm centre bolt through fixing escucheons. Latchbolt is brass, roller bolt to suit either hand. Projection is 12mm. The measurements are as follows: 101mm(A) lock comes with 57mm(B) backset