Automatic primary chain adjuster?

[BeDaring08]

I was thinking about installing a automatic primary chain adjuster on my 07 blast. My only question is what primary is our primary based on? Is it twin cam primary, sportster, ect. Here's what I'm looking at and I'm not sure which one to get. I don't mind modifing it some if need be. HB Wedge Hydraulic Automatic Primary Chain Tensioner*

[Theycallmecrash]

Thats how the factory tensioner works. It only loosens when you choose too.