You can also get the Modify spring guide. A bit cheaper and it is the same overall.
They also usually have the MASK piston heads...
Here:
http://www.airsoftparts.ca/store2/in...oducts_id=1184
Also, you might want to install that head instead to reduce the impact. It is made to be used with the MASK piston head:
http://www.airsoftparts.ca/store2/in...oducts_id=1318