One, 5" diameter 6061 billet aluminum resin fiber disc backing pad (1/4" thick) at pad, (3/4" thick) total. Intergraded with twelve venting pockets to allow proper heat dissipation, extending the life of your resin fiber discs! Using aliminum over plastic means a harder backing pad with no difflection when under pressure. Say goodbye to replacible plastic backing pads that have a limited lifespan. Our 6061 Aluminum Backing Pads will last if cared for properly. But not to worry, this is a replaceable product as your existing plastic backing pads. This product is perfect for all applications varrying from wood to metal. Allowing for a reliable rigid product over and over again!