LTV4 = inner diameter + .637" or 16.18mm
The LTV Model has a bit extra room in the walls of the cup than the LT model has. This special design of the cup, coupled with a tight #28 bore (.140 or 3.57mm) combined with an efficient back bore and the longest overall length in the line makes the LT design the top screamer of the Studio Master Series...if resistance is truly your friend!
