I am not sure. I believe the RCXP is an updated design made especially for RC Extreme power, and is supposedly 30% smaller and 30% lighter than the RCEXL ignitions. Reports on its function have been very good. You will need to verify voltage requirements with your supplier to be sure, but I know the RCXP is good to at least 8.4 volts. I believe the RCEXL units have been updated to be able to use higher voltage as well.

The main man at RC Extreme Power goes by "BadAzzMaxx" here in the forums.

AV8TOR