So here is the idea........The tubes vary in length between models. There is a bulge on the tool just before the part that goes into the oil (dipstick part". The tool gets pushed down until that bulge reaches a restriction (can't go any further)where the tube enters the transmission. This places the "dipstick part" into the oil. When hot, the "dipstick part" is covered almost to the bulge. Here is a reference pic of the tool the numbers don't really man anything. There are all kinds of them out there, but all have the same idea. I have a drawing of the relative measurements that I will try to find and post.