The glass tube used with the SF-77BLT system is larger and able to accommodate larger tubing and therefore larger volumes and faster flow rates than the glass tubes used with the SF-77B and SF-77BST systems.

The ML series manifold is used in the SF-77BLT system because the output port can accommodate the tubing (PE-50) that fits into the bigger glass tube used in this system. 

The MM series manifold is used in the SF-77B and SF-77BST systems because the output port consists of the tubing (PE-10) that fits into the smaller glass tubes used in these systems.