Internally expanded, permanent (requires special machinery for installation), plated steel Scovill-type couplings are used on "small ID" cement, plaster, grout & shotcrete hoses where a standard barbed fitting reduces the flow and can clog small diameter hoses. For larger diameters swage or external crimp type fittings are normally used for concrete, plaster, or grout as "internal expansion" fittings cannot be heat treated and will wear out quickly. Assemblies used in critical applications must be tested/certified at regular intervals. Do not repair cement, plaster, grout hoses due to tube wear, which results in coupling retention problems if attempting to repair.