XT panels have larger grit for faster results. 6” pipe: Hub 6” for 6-8” Pipe - 1/2 Shaft (1001240150A) & 6” Hub (6-panel) (1001870150A). 6” and 8” pipes: use with Hub 6 & 8” (6 Panel) - 1/2 Shaft (1001250150A). Sold in packages of 12 panels.