Variable load control knob gives full range of adjustments. NO. 400 Heavy Duty Base handles larger, heavier objects than the No. 300 base. Accepts only the No. 437 Head.
Big Book Catalog, Issue:65, Page:439
SPECS: 4-1⁄8" (10.5cm) square, 3¼" (8.3cm) tall. 1.5 lbs. (680 g).