Seal-X XP is a trowel-grade mastic designed for a variety of surface preparation and detailing work with UltraSeal XP and other Cetco active waterproofing membranes. Featuring XP Technology hydrophilic polymer, It swells upon contact with water to form a watertight barrier in fresh to high saline water conditions. Seal-X XP is easy to apply and bonds to most building materials with the consistency of thick grease.