Which of the following equipment/accessories is legally permitted in a volleyball match?

In volleyball, the rules regarding accessories and equipment are designed to ensure player safety while also maintaining the integrity of the game. Hair devices made of soft material and no more than 3 inches wide are legally permitted because they help players manage their hair without posing any risk of injury to themselves or others. Soft materials are less likely to cause harm if there is contact during play, making such hair devices appropriate according to regulation guidelines.

Altered knee braces can pose a risk, especially if they modify the brace's function or introduce hard materials that could potentially cause injury. Unpadded hard items on the wrist are not allowed because they present a danger to players in the case of contact. Thus, the only option that adheres to safety regulations and is allowed in a match is hair devices made of soft material and of an appropriate width.