A Velcro disc, also known as a hook and loop disc, is a type of sanding disc that is designed to be attached to a power sander. The disc is made up of two parts: a backing pad and an abrasive disc. The backing pad has a Velcro-style hook surface that attaches to a Velcro-style loop surface on the sander.

The abrasive disc is available in a variety of materials and grits, such as aluminum oxide, silicon carbide, or zirconia alumina, and can be used for sanding, polishing, or grinding various materials like wood, metal, plastics, and composites.

Velcro discs are easy to attach and remove from the sander, and can be reused multiple times. This makes them a popular choice for professionals and DIY enthusiasts who require a fast and efficient sanding process.

Overall, Velcro discs are a versatile and convenient sanding option that can provide high-quality results with minimal effort.

Here is a general size & Grit chart for velcro disc :

Size:

• 4 inches: This size is suitable for small sanding and polishing tasks and can be used with hand-held power tools.
• 5 inches: This size is commonly used in metalworking and woodworking industries for sanding and finishing applications.
• 6 inches: This size is suitable for larger surface areas and can be used for sanding and polishing tasks on various materials.

Grit:

• Coarse (40-60 grit): This grit is suitable for aggressive material removal and can be used for sanding and shaping tasks.
• Medium (80-120 grit): This grit is suitable for smoothing and blending surfaces and can be used for finishing tasks.
• Fine (180-320 grit): This grit is suitable for polishing and refining surfaces and can be used for finishing tasks.

It’s important to select the appropriate size and grit of Velcro disc for the specific application to ensure optimal performance and a high-quality finish.