Obsidian Air Universal Donuts Mouse Skates - Less Noise, More Control. Universal Donuts with diameter 9.5mm, offer better control and stop, less noise. Which surface is hard and finely frosted texture, effectively increasing the friction of the surface, especially hardened PTFE increases the braking power of the skates, allowing better control and emergency stop. Which is suitable for cloth mouse pads & glass mouse pads, not for Coating or plastic mouse pads. Added microporous polyurethane foam, make absorbing noise and mouse slide quieter. Offer better control and stop. More stable movement and less noise. Package Included: 32 donuts skates Two alcohol Pads Two adhesive remover wipes DIY Tip: Fewer dots provide greater speed. Conversely, more dots slow down.