【Function】This Aluminum Master Base Plate is designed as a machine accessory, it’s act as a backer-disc sit into the Grinding Machine and the top face for place grinding papers/discs/pads. 【Application】This Master Base pad is suitable for the Grinding Polishing Machine with 6” grinding pad. 【Advantage】This Aluminum master lap is Premium workmanship, accurate dimension, well made and plating, soften the sharp edges avoid hurt hand and for comfortable hold. 【Materials】100% Aluminum. KINDLY REMINDER that this Aluminum backer-disc is no diamond coating, it can't be used to grinding stone/knife/gem/wood and all other items directly. 【Dimension】Dia x Thickness: 6" x 9/32". Arbor Hole: 1/2".