C.R. LAURENCE 33SBL CRL Black 33S Silicone Sealant. This is our most popular sealant! CRL 33S Silicone is a high quality sealant that delivers the performance you demand at a competitive price. It is a one component, room temperature curing, acetic cure, 100% silicone elastomer that does not require the addition of activators, stabilizers, or catalysts to achieve optimum performance.. Part Numbers Variations: 33SBL