Compression Male Adaptor Fitting This male adaptor fitting connects between a length of MDPE pipe and a female threaded fitting, but still provides a strong and secure joint. To maintain a rigid and reliable joint connection, it is highly advised that a pipe liner (also known as a stiffener or insert) is also used. Material: polypropylene Compression fitting BSP thread Sizes available from 16mm x ½" to 110mm x 4"