Ghost O-rings by Paul Yath
Paul says they ...are clear silicone o-rings that fit into YoYoJam yoyo's. They offer the play of a flowable silicone yoyo but last longer and you dont have to go through the mess of applying it and letting it dry.
Price is per o-ring. Fits YoYoJam yoyo's.
These are not flat, they are round (doughnut-like) in shape. Push-fit.
Approx 14mm ID, 19mm OD.