The special hex shape of this dumbbell prevents rolling away from the storage place or during your floor exercise, while rubber coating also reduces noise and protects your delicate workout area.Made of high quality solid cast iron core to add more durability & stability. Will not break or bend after repeated use. The special hex shape of this dumbbell prevents rolling away from the storage place or during your floor exercise, while rubber coating also reduces noise and protects your delicate workout area.Made of high quality solid cast iron core to add more durability & stability. Will not break or bend after repeated use. The special hex shape of this dumbbell prevents rolling away from the storage place or during your floor exercise, while rubber coating also reduces noise and protects your delicate workout area.Made of high quality solid cast iron core to add more durability & stability. Will not break or bend after repeated use.