ZETA rides dirt bikes. ZETA develops products for dirt bikes. They test, manufacture and supply high-quality products for dirt bike riders. Their product ideas come from their riding experience, from professional riders and from MX factory teams. You must not miss ZETA products for your ride! Replacement free piston kit for KYB AOS Twin Chamber forks. Made of lightweight aluminum, much more durable than the O.E. plastic piston that is susceptible to cracking. STD piston mimics the O.E. suspension feel. Plush piston provides a softer smoother feel throughout the suspension stroke.