The T Series was designed to be used as a cap or a plug and are tapered to fit a wide range of applications to protect from contaminants and debris. These caps/plugs may be used for mil Std, sae-type fittings, hydraulic and threaded or non threaded fittings. The tapered design allows the opportunity to cover a vast range of cap or plug applications. Easy to install or remove.:: a: 3.93, b: 4.07, C: 3.86, D: 4, E: 0.75, F: 4.38.