sorry about poor photo quality; I am pretty sure these are the Sliding Door Roller, 1-1/4" Steel Ball Bearing
Product Code: 81-033
stamped on side - Del Mar Eng CO.
wheel size- 1 1/4"; 1 1/8" tall; 3/4" wide; 1 3/4" long
single wheel at each frame end..
thanks for the help
Tom from SWISCO responded:
April 18, 2014
Thank you for the images. I agree, this looks a lot like our 81-033. Just double check your dimensions to make sure they match.