Sturdy galvanised steel for a lifetime of service. Stores F-clamps together efficiently and conveniently while mounting clamps firmly to the wall. Pre-drilled holes are 406mm (16") on centre for simple mounting to wall studs. Spacers between clamp storage slots measure 33.8mm (1.33") wide. Clamp storage slots measure 7.7mm (0.30") wide. Overall length 610mm (24") .