It is what it says it is, a perfect fit set of replacement o-rings for Grimmspeed's awesome AOS. The original o-rings had begun to deteriorate after about 5 or 6 years. Before I installed Grimmspeed's AOS, I used to have to add half a quart of oil between changes, and I drive a relatively low mile Subie. Where's all that oil going? Through the intake a lowering the octane rating of the fuel. After the installing the AOS, I have never had to add oil to the engine between oil changes. The level stays pretty much the same.