We now have back in stock the SINGLE spiral levers for the oldest 3020 Bogen tripods. These are different from the later models that had the DOUBLE spiral levers. They were never compatible, and because of the depth and curve of the single as compared to the shallowness of the doubles.
So if you have one of the old 3020, 3021 or 055c, 055a, 055b tripods from the early 1980’s you need the SINGLE SPIRAL.
If you have the 3021 or 055’s from the 1990s you need the DOUBLE SPIRAL.
In both cases, these parts are plastic and can be broken if you are over tightening them when you install them on the lock, or if they become fouled with dirt and grit during use.