C.R. LAURENCE 445805 CRL Limestone Vulkem 45 SSL One-Part Semi Self-Leveling Polyurethane. CRL Vulkemr 45 SSL Polyurethane is a one-part moisture curing, low modulus polyurethane sealant especially developed for sealing joints in level and/or slightly sloped surfaces. Exceptional wear and tear resistance in high traffic areas.. Part Numbers Variations: 445805