I don't have a mm measuring tape or anything. I bought an ashcatcher for a j adapter and thought the j was 18mm. I don't know size of ac either it might be 18.8 but I forgot. So how can I tell if it's 18.8 18 or 14
I picked up on size difference by sticking my pinkie in the downstem for the female adapters. If you can only fit the first portion of your pinkie in, it's a 14mm. If it goes to the second pinkie bone, it's an 18mm. For male adapters, I guess just rule out the larger from the smaller.