[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. [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]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. [Applicability]Diamond coated flat lap disk grinding wheel can be installed on the aluminum master lap. So if you want to sharpening the gemstone or steel knives, you need purchase a diamond disk( Not included, need to purchase separately), and a aluminum master lap. Product Name:Aluminum Disc Master Base Lap Plate [Product SIZE]Diameter: 6 inch(150mm), Arbor Hole: 1/2 INCH(12.7mm) All our diamond flat laps wheels have a 1/2 inch arbor hole and are intended to be mechanically clamped to a Master Lap.The surface of the aluminum plate is smooth and the concentricity is good.We recommend using the Aluminum master lap for diamond coated flat lap disk. Note:Please make sure our product fits your equipment before you place the order.Thanks for your understanding! Material: Aluminum colour: Silver Package Contents: 1 x Aluminum master lap Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.