I used the Extreme power systems 2.4 as it was the first to offer modules & Rx's. I had lost a couple of jets on 35Mhz. I fitted it to my Avonds F15. For many flights there were no issues. As more people started to switch over to 2.4, I started to get the odd lock out lasting a split second. The lockouts became more frequent, so I ditched the system & bought a Spectrum module & Rx's. I have had no problems since.