Red Color Silicone 40A O Ring - China O-Ring, Auto Parts | Made-in-China.com
Amazon.com: 200pcs Rubber O-Ring Keyboard Switch Dampeners Make Your Mechanical Keyboard Quieter with Keycap Remover Suitable for Cherry MX Key Kit Dampers 40A-L-0.2mm Reduction (Transparent) : Electronics
Parallel Keyboard O-Ring – Parallel Limited
Rubber Ring Keyboard Switch | Rubber Ring Switch Cherry | Ring Dampeners Keyboard - Gaskets - Aliexpress
Glorious sell 40A/70A O-Rings at both 1.5 and 2.5mm for $10. Thought I'd mention this as usually people only talk about WASD. (link in comments) : r/MechanicalKeyboards
X1 Tools R-22 O-Ring (ID: 28 mm, CS: 3.5 mm, OD: 35 mm) (40 O-Rings), 40PK X1E-CON-ORI-RUB-0022x40 | Zoro
125pcs MX Cap Keyboard o ring 40A Switch Dampeners Cherry Rubber o-rings Red / Blue O Ring Replace Part