Flexible Shower Tray Upstands Seals are an invisible upstand seal used for sealing a shower tray/pan or bath tub. Flexible Shower Tray Seals are for those people installing a new shower tray or bath who prefer an exposed silicone joint to an extruded profile, Flexible Shower Tray Seals help remain a watertight seal in the event of the silicone seal leaking through joint movement or natural deterioration. At rubberduck Bathrooms we offer both AquaStrap and ClassiSeal Flexible Shower Tray Seals.