Transition fitting

This fitting is used to connect a pipe with an alarm component with an inner thread of 1/2".

The diameters are 14 x 2, 16 x 2, 18 x 2 and 20 x 2, certified and 0 x 1,3, 14 x 2, 16 x 2, 16 x 2, 17 x 2, 20 x 2 and 20 x 3,4, uncertified.