This product fixed my Matrix SVD gen ll's lousy hop up. I have to admit, I was spectacle about how easy this would install. But trust me it's easy. This is basically the Chinese clone of AirsoftPro's A&K hopup unit. AirsoftPro has some great installation videos. I recommend using a Prometheus m170 spring with this and .4g bbs. I use this setup and the range and accuracy is nothing but impressive. Plus it stops the SVD's famous double feeding issue!
Fairly easy to install
Replaces the crappy stock hopup unit
Hopup can be adjusted without taking off the top cover
Stops double feeding issue
Some assembly required
Doesn't come with a hopup rubber (o well)