Disposable Arm Sleeves Covers, Waterproof Durable PE Oversleeves Covers Protector Disposable Sleeves for Arm

Bought for sterile work in a glove box. They tear easily, but as long as you're careful opening them they work fine.

These appear to be made to fit the arm of a child. Contrary to the product photo, they are very short, just barely reaching to the elbow on an adult and the arm openings are too small to fit over most adult arms.