TCB Bicycles brings the first American-made Titanium 650b mountain bike frame to the market today. So what is 650b and why is the whole bicycle industry abuzz with all talks about 650b? 650b refers to a bicycle's wheel size that is approximately 27.5" in diameter that fits right in between the two most common mountain bike wheel sizes: the traditional twenty-six inch and the twenty-nine inch known as the "twenty-niner". A 650b wheel provides riders with a middle ground and offers advantages from both ends of the spectrum, including the agility of a smaller twenty-six inch wheel and the stability and traction of a larger twenty-nine inch wheel.