Customized Keychains & Keylights, Round Ball - Stress Reliever Key Chain - Polyurethane, Round ball stress reliever with a key chain, 1 1/2" diameter. Due to their handcrafted nature, stress ball sizes, colors and textures may vary. Factory cannot guarantee consistent imprints or PMS matches. Material: Polyurethane. ... #LKC-SB03 $1.40/each.