The models 504/505 are orbital sanders with a 3/32 offset. The smaller rectangular orbit allows better sanding access for bumpers, recessed areas, and new panel prep. Both sanders use standard 2-3/4 Velcro sandpaper rolls. Velcro pads securely hold scuff pads for easy new-panel prep. Built-in pad release feature. Models 504 2-3/4 x 4 Velcro pad models 505 2-3/4 x 5-1/2 Velcro Pad. .