This makes your prep time faster and IMO a bit safer if you use the clear tubes like Lanes. You can verify them by a quick tap down and compare the graduation marks. I TRIPLE check all SML loads and i am extremely careful with my witness marks. The Knight/Lehigh Ultimate range rod REALLY helped out with that part.

http://www.youtube.com/watch?v=KwGrlzrVAC8

It even works with BH209 but no other subs.