The Vulkem I ordered had a rather grainy texture which started to crumble a year later. ParBond seemed easy to apply along the top side of rub rails but seemed to crack in numerous places after a year. I've been happy with Silkaflex but it has only been 8 months since I put it on the trailer. It seems to have kept its rubber-like property.
'01 2500hd ext. cab, 8.1 litre gas, 5 sp. Allison auto
3.73 rear end
Mag-Hytec rear diff cover
Amsoil Dual by-pass oil filtration system
Amsoil synthetics all around
265 watt AM Solar, Inc. system