The Rock Band Precision Bass (known as the 'PBass') is an officially-licensed Rock Band controller, produced by Mad Catz.
It features a thumb-rest and a "split" strumbar to allow for double upstrumming; one can pluck the bass strings like they would on an actual bass guitar. The side-effect of this unique design is that you can strum incredibly fast by alternate-strumming both at the same time.
Unlike any official Rock Band Stratocaster/Jaguar, all four switches of the split strumbar click. It is one of the only officially-licensed RB controllers to have physical switches in the strumbar.
It features a longer neck than other Rock Band guitars with quick-action frets, as it is meant to be a partial replica instrument. Tapping is incredibly difficult to do on this.
Finally, it comes in two forms: there is a wired 360 variant which is uncommon to begin with (only 10,000 were ever produced, according to the sticker on the back), and there is a wireless 360 AND PS3 variant, which are considered to be much rarer. The wireless 360 and PS3 variants are very sought after as they are compatible with RB4 on the XB1 with the Legacy Wireless Adapter, and on the PS4 with the PS3 PBass's dongle.