When your tripod is not equipped with an accurate spirit level, this convenient plate fits between your BH-40 ballhead and your tripod platform and gives a true level reading for the base of your ballhead.
 
BH40-LVL features:

• Fits snugly between your BH-40 ballhead base and the tripod platform.
• Includes an accurate 15mm acrylic circular spirit level sensitive to 30 minutes of angle.
• CNC machined from 6061T aluminum.
• Individually calibrated on super-level granite surface plate.
• Degree marks on BH-40 panning base remain visible.
• Use with any ballhead with base diameter no larger than 2.0" (50mm).
• Use with any tripod with platform diameter no larger than 2.5" (63.5mm).
• NOT compatible with our BH-40 LR II ballhead (clamp is too large to clear the rim of the BH40-LVL when clamp is flopped over into the drop notch.

 
NOTE: You must be able to count at least 4 threads of the 3/8-16 stud protruding above the tripod platform (and no more than 6) in order to use this plate safely.
 
Height: .425 inches; (10.8mm)
Base Diameter: 2.47 inches; (63mm)
Tripod Mount: 3/8" 16
Weight: 1.0 oz (29gr)