The all-cast iron dovetail structure not only makes Snode adjustable dumbbells drop-proof and durable, but can also makes dumbbell plates be structurally linked to each so that they will not fall. Regarding the structure of our adjustable dumbbells, the inner rod in the center is not stressed, the stress point of our dumbbell AD80 is our uniquely designed dovetail groove, that is, the trapezoidal groove on the dumbbell plate, and the rod only plays the role of adjusting the selection.