it's not it's 20-21mm. I may have to re-drill some holes in it if the strings themselves don't push all the barrells together. it could be 19mm if super tight. But overall it's heavy weighing .225kg (with screws) and feels solid.

Ive been using this bridge for my custom bass guitar. I installed it 5 years ago and with daily playing its still holding strong and looking sharp. I like how i get choice to put string through body altho i never used it.
After 5 years no sign of rust or patine. I would buy it again.