If you've got a bike frame with a 49mm ID head tube, it will accept a fork with a 1. 5" steerer tube. But it also leaves you plenty of opportunity for use with other steerer tube dimensions as long as you use the right headset. This Chris King InSet Model 5 Headset will allow you to mate a fork with a 1-1/8 to 1. 5" tapered steerer to your bike. And since it uses King's low-stack InSet top cup, you can get your stem a bit lower if you like (a good thing for smaller riders on long travel bikes). This Model 5 Headset benefits from Chris King's GripLock upper bearing cap. This assembly replaces the older style, one-piece bearing cap that contained the O-ring. Instead, GripLock uses a split ring to center the steerer tube in the upper bearing, and when you preload the assembly, the split ring provides additional surface area against the steerer for a more secure and safer interface, especially on carbon fiber steerer tubes. We'd consider this to be a mixed headset because the upper bearing cup contains the bearing within the head tube. In contrast, the lower bearing cup houses the bearing outside of the head tube. We're big fans of tapered steerer tubes because of the perfect balance between light weight and steering stiffness. The traditional lower cup allows the larger 1. 5" bottom bearing, giving you precise steering and a bulletproof system, not to mention that the fork can be built with a stronger, stiffer crown. The Chris King InSet Model 5 Headset is available in eight polished-to-perfection anodized colors - Black, Navy, Red, and Silver. The base plate can be exchanged for one that fits 1-1/8" straight steerers (sold separately).