Oz-Hammer - Driver for Jackhammer: Oz-Hammers are REQUIRED for customers that want to drive the Oz-Posts in the ground with a jackhammer. Some Oz-Posts require Hammer-Spacers to be used in conjunction with this driver. Please see the list below or the Oz-Post product specifications. Please see additional information under Oz-Hammer OH-01. Specifications: 1 1/8” hex chisel holder with a retaining collar. For use with (no Hammer-Spacer required): GB-700 Hammer-Spacers required for Oz-Post Models: HB-700 and C175-850