If you're in Columbia, shoot over to Shop Rd., exit 5 off I-77. There's a place called the "Hydraulic Shop", next to NAPA. They sized some O-rings for me. They knew everything there is to know about O-rings, Durometer scale, material, et cet. I got a set to rebuild a SLS pump (except the MB unique seal) for $1.90. Very nice folks !