Kyosho UMW708-02 5.8mm POM Flange Balls 4pcs

These are 5.8mm flange balls molded in POM, supplied four to a pack, and they are the service part for Kyosho's UMW708 rear stabilizer set on the Ultima RB6 mid-motor chassis.

The flange ball is the pivot that connects the stabilizer bar linkage to the suspension arm, and it has to rotate smoothly under load while staying tight enough that there is no free play in the system. Any slop here shows up as a delay between the suspension moving and the anti-roll bar actually doing its job, which makes the car feel vague on turn-in.

POM, the same acetal material sold as Delrin, is chosen because it is self-lubricating and holds its shape under repeated loading, so the joint stays smooth without needing grease and resists the wear-in that opens up play over a race weekend. These are wearing parts and are worth replacing whenever you notice the stabilizer linkage has developed movement. Four balls are included, enough to rebuild both ends of the bar. This is a direct replacement for the balls supplied in the UMW708 set.