A1 Top Extension(not a stock item)
A2 Threaded Spigot
A3 Stud Tightening Turnbuckle (not a stock item)
A4 Extension Tightening Knob (not a stock item)
A5 Clamp Assembly(not a stock item)
A6 Brake Shoe

B1 Boom Arm (not a stock item)
B2 Upper Pole (not a stock item)
B3 Bottom Pole (not a stock item)

C1 Control Knob only
C1 Control Knob w/ Washers and Bolt

D1 Pole Locking Knob (not a stock item)

E1 Upper Leg Brace Lock Knob

F1 Upper Leg Brace Lock Knob

G1 Spider Assembly

Editor note: All 420b Versions are interchangeable. The parts number changed between models, but the functionality did not change. Click on the numbered link to see the actual part picture.

See 420B ver 5
Manufacturers Parts List See 420B ver 6
Manufacturers Parts List