This kit of 6 round fiberglass rod ends and the hardware will convert your original Multi-Frame for wood 2x2s to a frame that can use round metal pipe. Some folks are calling this the "upgrade kit".
Good instructions are included including an exact description of the pipe you need.
These round rod ends come with the Multi-Frame now. You may want to buy and extra set, but it is really easy to just move the rod ends from long to short to long, etc.
1"x3"x4" 12 oz