The highest quality pivoting stem system available. Nylon pivot interface prevents wear and gives smooth operation. Side load is adjustable with a 5mm allen wrench.
Steerer tube outside diameter refers to the fork tube coming up through your frame that the stem mounts to.
The riser tube is the long stem tube coming up to your handlebar mounting. The inside diameter of Rans and Bacchetta short wheelbase bikes are 1", whereas HP is 1 1/8" and Rans Xstream long wheelbase bikes are 1 1 1/8, so choose your specs carefully.