Generally
An extra long nipple for 1/4″ brake pipes, this nipple fits brake pipes that have an outer diameter of 1/4″ = 6.4mm. The nipple outer dimension is 7/16″ approx: 11mm if you measure with a caliper. Check the dimensions carefully, it is not always the same dimensions on all nipples for a brake system. The threaded part of the nipple is 16mm.