Hex and round dumbbells are fixed-weight dumbbells for use in commercial and in-home gyms. Both types of dumbbell are made of cast iron and offer a large selection of weights. However, hex and round dumbbells have different designs and features, each with advantages and disadvantages in the weight room.
A round, also called a pro, dumbbell consists of a handle and standard weight plates. An Allen bolt holds the weight plates to the handle and an end cap covers the bolt. A hex dumbbell has two cast iron heads, each with six sides. The handle and cast iron heads are welded together into one piece. Both types of dumbbells are made of cast iron. Hex dumbbells have a painted enamel surface and pro style dumbbells have a flat finish.
Because hex dumbbells are welded together as one piece, there is very little give to the dumbbell. If you drop the dumbbell, the weld may snap, causing the dumbbell to break. If a hex dumbbell breaks or becomes loose, you have to throw out the entire dumbbell.
A pro dumbbell has more give to it. It can withstand more stress because it gives a little. If you do break a round dumbbell, you do not necessarily have to throw it out. You can take the dumbbell apart and just replace the piece that broke.
The painted surface of a hex dumbbell is more likely to chip than the surface of a round dumbbell. If you accidentally bang the weights together at the top of a dumbbell bench press, you may have paint chips fall onto your face. You can put rubber end caps on the pro dumbbells to protect the plates if you do bang the weights together. Both round and hex dumbbells are available with rubber-coated plates. The rubber protects your floor better if you don't have carpet or a workout mat.
Because the heads on hex dumbbells have six sides, they do not roll. Round dumbbells will roll away if you place them on an uneven floor.
Hex dumbbells are available from 3 lbs. to 100 lbs. They increase in 3-lb. increments up to 15 lbs.; then they increase in 5-lb. increments. The lowest weight of a round dumbbell is 5 lbs. They increase in 5-lb. increments up to 150 lbs. or more.