As others have noted, these Croakies have a VERY small opening for the earpieces to enter.  I got them to put on my cycling glasses which have fairly small, flat ends on the earpieces, but even these wouldn't go in.  I tried wetting the earpieces, stretching the opening in the Croakies with a knitting needle, and a few other things.  Nothing worked.  The stitching that forms the opening in the Croakies started to unravel with all my efforts to get them onto the glasses.  Finally, I did what others have done - just tied the Croakies onto the earpieces.  Seems like a very lame thing to do, but it's not worth sending them back.  They actually work quite well this way and are very comfortable.  I suspect they look a little goofy, but what do I care when I'm cycling?  Unless the earpieces on your glasses are extremely small in diameter (no more than 2 mm, I'd say) don't get these.  Try a larger or more forgiving product.  I've had good results with Chums, but they are cotton and tend to start stinking if used during sporting or sweaty use unless you wash them regularly.  They also have a "tail" that dangles which some people find irritating.