Four string Bass from the Pro series. For the bassist that won't settle for anything less than the best, the Pro lineup represents the pinnacle of everything the BB designers have sought to achieve over four decades of striving for perfection. Carefully crafted one at a time by a select team of master artisans at Yamaha's headquarters in Japan, and featuring a unique Alder/Maple/Alder laminated construction finished with Yamaha's proprietary IRA (initial response acceleration) technology, the Pro BB offers a rich, organic tone and incomparable resonance and playability-this is the bass that you've always dreamed off.