The first decision you will need to make when choosing which forearm pads will work best for you is what you will be using these pads for. Football players commonly use these pads to protect the forearms, particularly linemen who will be colliding with other players frequently. Some types of mountain bikers may use forearm pads, as will people who do sparring in karate or other forms of martial arts. Determine what your protection needs are before purchasing, and don't forget to think about flexibility. Some pads will extend over the wrist and hand, limiting mobility.
The two basic types of forearm pads are hard shell pads and soft pads. Hard shell forearm pads are usually made of plastic, and they are designed to withstand impacts from hard objects. They can be secured to the forearm with hook and loop straps, or with sleeves that slide over the arms. These forearm pads are a good choice for downhill mountain bikers and any other athletes who will run the risk of colliding with hard objects. They are not the best choice for football players, since these types of pads are likely to be illegal for use in games; the hard shell plastic can end up injuring another player, so football players will usually need soft pads.
Soft forearm pads usually feature a sleeve that slides over the forearm. One side of this sleeve features thick padding that protects the forearms from impact during athletic activity. When choosing among these types of forearm pads, you will need to decide whether you want a forearm pad that runs from the elbow to the wrist, or if you want a pad that runs from the elbow to the knuckles of the hand. The latter style may limit some mobility of the hand and arms, though some feature gaps in the padding at the wrist to allow for more mobility. Try to choose a pad that is lightweight and one that will not overly limit your mobility during athletic events.
some forearm pad models are sport-specific. Hockey pads, for example, feature a hard shell exterior with a softer lining. The pad usually extends from the forearm near the wrist all the way over the elbow to the upper arm, and it is often hinged for flexibility at the elbow. The pad is secured in place using hook and loop straps. If you are participating in a sport that features pads designed specifically for that sport, be sure to research the different models available within your budget and needs.