Tacoma bedrail caps have textured, raised ridges creating an uneven surface for the weatherstripping of the BAKFlip MX4 to rest on. This creates gaps, preventing a good seal and allowing water to flow freely underneath the weatherstripping into the bed. I used 1/16" adhesive foam tape, cut to fill the gaps, and cut flush to the edge of the weatherstripping. This turned out to be the perfect thickness for the weatherstripping to lay flat and solved the problem.