Didn't have to do anything to them. They do fit really tight and I thought I might have to do a little sanding, but didn't. Had the dark ones on my M15 for a while. Thought they were too dark for the gun but I really shoot it good with them so since the new ones are lighter I tried them on the M15. I think this is where they are going to end upJust a stunning grain .. was it much work to fit them?