Our pistons are a direct fit for your Rammer S21. The OEM part number is 200139.
Big Hammer Co is an aftermarket manufacturer for all the brands we sell. Big Hammer Co is not endorsed or sponsored by, or in any way associated with Rammer. This product is an aftermarket part.
Any use of or reference to the Rammer trademark is for the sole purpose of indicating compatibility or product fit, and is not meant to imply any affiliation or relationship between Big Hammer Co and Rammer and/or the Rammer Trademark.