The new Vampower RP4S1 is the world's smallest and lightest 4 channel synthesized receiver. These are perfect for any model from small foamies to bigger electrics. And because it's synthesized, you won't ever have to worry about crystals again! The new RP4S1 maintains the same high quality you've come to expect from Vampower. Try one (or more) today. You'll be glad you did! This receiver will only work with a 4 or more channel radio running in FM / PPM mode on 72mHz. If you have PCM, there is a probably a setting somewhere to change it to PPM.