Trial Lens rims are colour coded to power
All Trial Lenses fit to a modern trial lens frames
All lenses are marked on both sides - so you don't need to think about right and left lenses
Cylinder Lenses have Axis Markings on the Lens rim This means that you can be sure that the cylinder axis on the lens conforms to the marking on the Lens rim
It also means that the Optical centre of the Lens is at the geometric centre of the mount.