Award winning Self Adhesive Waterproof Upstand Accommodates Up To 15mm Of Movement Blue 4m Classi Seal Flexible Waterproof Upstand for Shower Trays and Baths 4 Metre The classi seal provides consistently effective waterproofing in any bathroom with a bath or shower tray installation. the seal can easily be applied to the wall-touching sides of a bath or shower tray, prior to final plumbing and tiling. it is suitable for new build, repair, or renovation.