A slap bracelet (or snap on bracelet) is a a layered and flexible stainless steel material coated in soft pvc vinyl with a velvet backing for confort. Stainless steel section of the wristband is call a bistable spring band.
The bracelet can be straightened out, creating tension within the springy metal bands. The straightened bracelet is then slapped against the wearer's forearm, causing the bands to spring back into a curve that wraps around the wrist, securing the bracelet to the wearer for a great promotional touch.