After purchasing a Printrbot Power Tower, I found that only the wooden spools work on it. I decided to create these extensions to hold the spools of filament I was getting from Ebay. They work great with the spool hub adapters that I create.Designed in Sketchup and printed in ABS with supports. Prints on its side to give the slots more strength where they slip onto the power tower. Print (2), one for each side.