The first thing you need to check when purchasing a new fork is the brake mounts and steerer tube. The fork needs to be compatible with the current setup. The majority of current bikes require a straight 1 1/8” steerer tube or a tapered steerer tube. Older bikes may need a 1-inch steerer. Most bikes have caliper brakes. However, disk brakes are steadily gaining popularity. If you have brake discs, you need a disc compatible fork. All these factors will determine the right fork size for your bike.