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:

1. Fits snugly between your BH-40 ballhead base and the tripod platform.
2. Includes an accurate 15mm acrylic circular spirit level sensitive to 30 minutes of angle.
3. CNC machined from 6061T aluminum.
4. Individually calibrated on super-level granite surface plate.
5. Degree marks on BH-40 panning base remain visible.
6. Use with any ballhead with base diameter no larger than 2.0" (50mm).
7. Use with any tripod with platform diameter no larger than 2.5" (63.5mm).
8. 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.

Specs:

1. 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.
2. Accommodates ballheads with base diameters no larger than 2.0 in / 51 mm
3. Weight: 1.0 oz / 28 g
4. Height: .425 inches; (10.8mm)
5. Price: $45