It's a rattle, dumbbell.

Buff Baby turns Junior into a bench-pressin' body-builder! Your little one's curiosity will be piqued by the gentle rattle sound and natural hand-grips, while your sense of irony will be satisfied by watching Junior do 3 sets of 10. So...work it, baby! 5 1/2" x 2", no phthalates, no BPA, safe for baby.