Made of hard rubber to stand up to hours of use, Zanies® Hard Rubber Star Explosions also feature a surface of gum-massaging nubs. They make dental hygiene fun! Zanies® Star Explosions are made of hard rubber to stand up to hours of chewing fun and feature gum-massaging nubs to improve dental hygiene. These fun dental toys will send dog to outer-space. Ideal for even the most aggressive chewers and teething puppies. Medium Red measures 4".