Slap bracelet

Consisting of layered, flexible stainless steel bistable spring bands sealed within a fabric, silicone, or plastic cover, it can snap around a wrist when slapped on it with some force.

Some knockoff versions used thinner steel, which was more likely to break and/or cut the wearer, the dangers of which first came to light in 1990, soon after they were released.

[1] It was a fad among teenagers and younger children in the early 1990s.

The bracelet was banned in several schools following reports of injuries from worn out or modified versions.

[2][3] In 2018, different slap bracelets were recalled: "The slap bracelet’s metal wristband can pierce the protective fabric around it and expose sharp edges, posing a laceration hazard to young children.