The Moog boot in the picture posted seals to the joint. The Delco joint looks to be an umbrella type seal. That was my point, the Delco should be a sealed unit like the Moog. In general the metal "bearing" that's in the Moog joint takes the grime better then the high impact plastic and Kevlar. I'm not sure why a Moog rep would tell you that if Moog makes the boot that seals. Maybe another case of the guy with a sales pitch that doesn't know the product.