8294700111 Mirka Multi Interface 77mm 6H 5m Single Pack, used in combination with Velco Hook & Loop sanding discs. Protects the backing pad, should be changed regulary : Amazon.co.uk: DIY & Tools
77mm 1/4" Thread Mirka Backing Pad
Backing Pad Ø 77 mm 1/4" - Mirka
Mirka ROS325CV 77mm Random Orbital Sander 2.5mm Orbit - PowerToolSalesUK.com