I just checked the tyga site.

http://tyga-performance.com/site/product_info.php?products_id=1339&osCsid=6484eb82fa5371c2adfc9536a364485a

I only have 3 bits.

No wonder I couldn't work it out.

Now i have to figure out if I lost the 4th bit or it never came with it....

Bought is some time ago and Have moved house since.