Strong galvanized steel ribbed rust-resistant frame holds a tapered die cast aluminium spool designed for ease of starting and wire alignment. Two extra teeth on spool provide easier wire tightening action and control, requiring less clip turning to hook into next tooth. Increased spool hub thickness provides extra strength to accommodate using up to .15748" (4mm) gauge fence wire. Easy to use upside down. Wire can be threaded through strainer instead of tying an extra knot High quality spring loaded locking clip. 5/8" (16mm) square drive. Cliplock operates with a smooth "clicking" action in any position. Strainer Handle Spring Ratchet (G69530) is required to tighten wire. Works on high tensile, barb and woven wire