Parth mentioned fitment was perfect. One way to demonstrate that is to view the lens from the rear with a polarized lens when looking at a light source. If the lens fits perfectly, then a polarized picture will clearly demonstrate an absence of stress bands. Conversely, a lens that doesn't fit perfectly will have rainbow color banding refractory patterns around the stress points of the lens/frame interface. It goes without saying that the periphery of the lens vision will be somewhat distorted if the fit isn't "perfect"