Rans Enduro Sport, Hase Kettweisel Tandem, Merin Bear Valley beater bike
1. Fork steerer size. Usually 1 1/8".
2. Handlebar clamp size. Usually 25.4mm for flat bars and 26.0mm for drop bars.
3. Angle - a tricky one 0 and 90 degrees are the same. Go from there.
4. Length - another tricky one:
Extension is the hypotenuse distance.
Reach is the distance parallel to the ground.
Make sure your that seller is using the same definition that you are. Most of the time the measurement they give you is the hypotenuse distance so you might have to do some figuring to determine what you really need.