One of the problems is that different color 1 3/8 thumb slugs have different OD's, thats why they came out with the larger sleeve. Not sure, but I think I may have been the one to call them up and alert them to the problem. The black ones always fit perfect, but the other colors are always tighter. After you glue in the sleeve, use your bevel sander to make the sleeve larger and you will not have any problems.