CleanSpace CST half masks (including a CleanSpace CST head harness) are designed for use with the CleanSpace PRO power unit (CST1002) and CleanSpace ULTRA power unit (CST 1012); the CleanSpace CST half mask is made of soft silicone that readily molds to the face and does not cause allergic dermatitis; the easy-to-locate clips secure the CleanSpace CST half mask to the power unit; the CleanSpace CST head harness attaches easily to connection points on the mask arms and can be removed for cleaning.