Bought timing chain & rails for my '84 300CD. OM617 Turbo Eng. The original main chain rail at the tensioner had a hard plastic coating on it. The replacement has a very hard rubber adhered to it. The supplier (Germanstar) told me they change back & forth over the years & it's German, it'll be fine. Though, can't see any brand on the aluminum. Anybody got any info? Seems to me it may be quieter, but less durable. Thanks, Paul.