Kyosho ORG04 P4 Silicone O-Ring Set 10pcs

A pack of ten JIS P4 silicone O-rings, nominally 4mm inside diameter with a 1.9mm cord.

O-rings this size are the sealing elements in small assemblies across a radio control car: shock caps and bleed screws, fuel and exhaust joints, and differential housings depending on the platform. They are pure consumables. Heat cycles, fuel, shock oil and simple compression set all harden them progressively until they stop sealing, and the failure is gradual rather than sudden.

Silicone is the reason to use these rather than a generic nitrile ring. Silicone stays flexible over a much wider temperature range and resists the heat cycling that hardens ordinary rubber, so it holds its seal for longer in the places on an RC car that actually get hot.

Kyosho colour-codes the ORG series by size, so the colour is an identification aid rather than cosmetic. Ten are supplied, which is enough for a full service with spares. Kyosho lists them across the Inferno NEO through NEO 4.0 including the VE variants, Inferno VE, the ST-RR and NEO ST truggies, Inferno MP-7.5 Sports, Psycho Kruiser VE and Scorpion XXL.