Sliding window rollers

OK - I ordered the part number 87-163 for our Sun City Palm Desert Atrium sliding windows, which looked like the correct part. It is the same size length and width. However the part I received has plastic bumps on the side that would go into the track of the window. The part that I am replacing is totally flat on the side that goes into the track of the window. The new part received (with the bumps) prevents the window from being able to go into the track to slide. Do you have a part that is similar to the 87-163, but totally flat on the one side? The is the backside - not the side that rolls. Also, on the rollers that you sent, there were two different parts. A couple of them had closed sides, and the balance had open sides. Thanks for your prompt response.