Cap Barbell 40-Lb. Adjustable Cast Iron Dumbbell Set for $29.77. Shipping is $0.97 for a total of $30.74 shipped. Here is a screenshot for your reference. The dumbbell set is made of solid cast iron with a baked enamel finish and adjustable with four 6 lb plates, four 2.5 lb plates, 2 threaded solid dumbbell handles, and 4 spin-lock collars.