This medium-duty, rigid plate caster is load-rated up to 300 pounds. Made of zinc, the mounting plate is 4 1/8 x 3 3/8 inches, the inside and outside bolt hole spacing measures 2 3/8 x 3 1/8 inches, and the mounting bolt has a diameter of 5/16 inches. The black, phenolic wheel is 1 1/2 inches wide and four inches in diameter. The replacement wheel number is 5-4-339.