These strong magnetic tool bars are made from a series of ferrite magnet inserts sandwiched between two 3/16" thick by 1" steel bars and enclosed with yellow plastic strips.
The maximum weight capacity or pull strength is 20 lb for a flat 1" wide object. In actual use, much depends on the amount of surface area that contacts the magnet and where the bulk of the weight is relative to the magnetic inserts, but these are not weak-kneed tool bars and will handle 3 to 5 lb round-handled tools easily.
The 13" length mounts on 8-1/4" centers and weighs 2 lb. The 24" length mounts on 16" centers and weighs 3 lb 14 oz.
Suitable for use in the shop or garage, or mounted on unfinished walls.