One Waterproof Protector for Arm Casts - approximately 17 inches long - also comes with the resealable bag and manual.

My 2 year old used the slings for approx 2 days, before ultimately getting a hard cast.
All of these items are for a large range of children. She had ample space, especially in the waterproof cover.

Toddler Injury Bath Pool Beach Immobilize