TST is a circular supply diffuser. The distribution pattern can be altered and the gap width is adjustable. The TST is a circular supply diffuser for ceiling installation. The two-part diffuser unit can be adjusted to provide the desired throw. A shielding device is included which can be used to alter the distribution pattern to a directional (180?) pattern. The TST is manufactured from galvanized sheet metal, with a white powder-coated finish. The TST is available with the following diameters: ? 100, ? 125, ? 160, ? 200, ? 250 and ? 315. This device can be used for extract air. The diffuser is installed directly onto the spiral duct and fixed with pop rivets. If the diffuser is fitted to a THOR plenum box.