Got two of these from Sixmm. One went into a ASG M15 URX-SBR, the other into Specna Flex M4. Simple fit with no modifications required. Easy reroute of power cable to rear (channel part of gearbox) into PDW stock, Specna required a little extension to get to end of buffer tube. 1.14J on 90 PSI on 6.02 x 230mm barrel. 16 rps. Excellent, affordable, super quiet and responsive trigger.