XT panels have larger grit for faster results. 6” pipe: use with Hub 6” for 6-8” Pipe 1/2 Shaft (1001240150A). 6” & 8” pipes: use with Hub 6 & 8” (6 Panel) - 1/2 Shaft (1001250150A). 8-9” pipes, use with Hub 8-9” (8-panel) (1021800200). Sold in packages of 12 panels.