One size fits most kids (normal size kids no more than 10 years of age, or older people who are really small). This set contains 2 wrist guards, 2 elbow pads and 2 knee pads.

Manufacturer's description:

R.E.D. Skate Wrist Guards:
Absorb impact, provide support, and protect your wrist thanks to an ergonomically designed nylon splint. Constructed from long life Cordura fabric, R.E.D. Skate Wrist Guards feature a 3-pull design with Velcro closure straps to provide maximum comfort, support, and adjustability.

R.E.D. Knee & Elbow Pads:
Both feature a low-profile design, yet provide big time protection. These proven skate park designs offer maximum durability, comfort, and protection. Constructed from long life Cordura fabric, R.E.D. Skate Park Pads feature ergonomically fitted inner foam, adjustable fit Velcro straps, and full coverage nylon hard caps. Perfect protection for the park from R.E.D. Skate.