Heavy Duty Aluminium Backer, Diameter 4" or 100 mm,with more wear-resistance and will not flex under pressure, perfect for flat surface wet or dry polishing Hook and loop backing pad made with premium grade rubber, semi-flexible backer Metal aluminium arbor with 5/8" 11 Thread, wear-resistant and applicable with most polisher or power tools. Wide applications, can use to connect wet/dry polishing pads, sanding pads, wool buffers, foam polishing buffers. Max RPM 4500 KEEYWOLT Diamond Wet/Dry Polishing Pads Metal Aluminium Backer-4 inch-Arbor 5/8" 11