Top Five Best Mechanical Keyboard O-Rings - Mechanical Keyboards Plus
CHERRY MX Rubber O Ring Switch Dampeners Blue 40a R 0 4mm Reduction 125pcs by WASD Keyboards for sale online | eBay
Keeping it (relatively) old school with my first semi-serious mech. WASD V1 with MX Blues, Black O-Rings, and Classic Beige and Grey Keycaps (thanks /r/mechmarket!) - Album on Imgur
Difference between 0.2 and 0.4mm O-Rings - Peripherals - Linus Tech Tips