If you purchase the above, all you need is an AEG hopup rubber & bucking (and the barrel obviously).
As far as performance, this is the second time my rubber has torn/misshapen causing for a replacement rubber. I have not had a chance to game the rifle, and only use it now and then for CAPS or target shooting. I think the fragile hopup rubbers are inherent design flaw with both the WA and WE GBBRs.
Below is a thread on gasguns that may be helpful also:
http://www.gasguns.info/forum/viewtopic.php?t=2171