More expensive, but a very strong locking system. Locks or opens with a simple twist of the inner leg. The best choice when one-handed operation is necessary. NR not available. Allows legs to telescope in and out, but not turn, keeping constant their relative orientation.
Helps eliminate unintended unlocking.
Simply pull in and out. Legs will not come apart. Popular style with positive locks. Opens of closes legs to predetermined hole positions. Style Fb includes silencing plastic bushings that provide a friction fit between sections.