First of all I am happy with the product. Glad I have bought it. Sadly the overall build quality of the smaller components are poor. For the trigger contact they used a 6,3 mm dowel pin to replace a 6mm fuse. Also the soldering of the wire to this pin came loose very easily. On the other contact the shrinkrap is to short to cover the exposed wire which will result in easy breaking of the wire. A final problem I had, but this could be because I installed it on a Well R4, is that the. 3d printed body was 1mm to long. The mags would not seat and if they did, they wouldn't feed. This was also a easy fix, but when I contacted Airsoftjunkiez they about the stated problems they did not respond. For a product this expensive the build quality could have been a lot better. Also no manual was included about the Jack and FCU.