Master Magnetics Round Base Magnet Fastener with 0.197" Center Hole Chrome Plate, 2.04" Diameter, 0.302" Thick, 35 Pounds, Silver (Pack of 6), RB50CX6 Magnet holds 35 pounds on contact with 1/4" thick, flat, smooth ferrous plate in a vertical test, 50% less on vertical surface holding against sliding force and less on steel with paint For indoors and outdoors applications at temperatures between -10 degrees and 200 degrees Fahrenheit Magnet assembly made of chrome plated steel cup containing Ceramic, Ferrite magnet Holding force is concentrated on rim of steel cup and will not hold through a layer of material Economical