ASI 502 is a 100% RTV Silicone that is UL & NSF Recognized. ASI 502 100% RTV Silicone is a non-slump sealant and can be applied to vertical or overhead surfaces without flowing or sagging. Because ASI 502 is a 100% RTV silicone sealant, it has excellent resistance to weathering including ozone, ultra-violet radiation, freeze-thaw conditions and airborne chemicals.