2 Meter  Mat Black Shower Head Hose Pipe Bathroom 1/2'' Stainless Shower Hoses. Bore size is inner Tubing diameter Not The hole Diameter on the nuts. Entery Hole diameter is 10mm. Inner Tube (inside the hose ) is 11mm in diameter. Exit hole (where nut connected to the hose) Deliberately made smaller than 10 mm in order to create pressure while it gets inside the shower hose to give you a better Spray)