Extra size and weight helps keep these blocks where you put them and the big face eliminates much of the "balancing act" when you're driving pins. Cannot mar even the most highly polished surface. Two different models. Green - For rifles and shotguns; drilled with four through holes for easier pin removal and disassembly. Convenient, center "V" holds cylindrically shaped parts steady so they won't roll. Blue - For revolvers and pistols. Larger through holes and partial "V" holds pistol barrels for easier link pin installation and removal. Can be drilled or modified with hand tools; will not melt when machined. Mfg: Brownells SPECS: Polyethylene, green or blue. 4" (10cm) diameter, 1-1⁄8" (2.8cm) high.