Like shown in this picture? The bike is a 1995 rigid MTB with a 23 inch frame, about the largest MTB frame you can find in a used bike, and I purchased it off of Craigslist, so no possibility of getting a 'professional fitting'. Its a Delta-brand extender that fits on a threadless steerer to give up to 3 inches more height. Larger bike shops and on line parts dealers sell them. It gets the handlebars up to a more comfortable height to make this bike a great commuter and all-around utility bike. I've had no problems with the extender coming loose.