ASP Palm Defender Heat (OC) pepper and Inert spray refill insert, developed by ASP, provides the same two million Scoville Heat Units or Oleoresin Capsicum (OC) protection as the original canister. The ASP Palm Defender Test (Inert) spray refill insert provides the ability to test your Palm Defender with its harmless inert spray. Operates in the same way as the original canister.