Really..
Four-bar suspensions and the Horst link
The four-bar active suspension utilizes several linkage points to activate the shock. A Horst link suspension has one pivot behind the bottom bracket, one pivot mounted at the chain stay, in front of the rear wheel drop-out (this pivot being the venerated “Horst link”[1] ), and one at the top of the seat stay. Some examples of Horst link four-bar designs include the now-discontinued AMP B-5, the Specialized FSR and related bikes, Ellsworth, KHS, Titus, and Merida.
A four-bar, seat-stay pivot suspension is similar looking, having a pivot above the drop out instead of in front of the drop out (ie no Horst link and no patent problem). Having the pivot in front of the drop out (i.e. on the chain stay) allows the linkage components to affect the path of the rear axle, thereby allowing for a more complex arc of the axle path. Placing the pivot on the seat stay (above the drop out) makes the rear axle travel path like that of a single-pivot bike, since the chain stay is the only component that affects the rear axle’s arc.
Seat-stay four-link pivot bikes perform exactly like similarly placed monopivots under acceleration and chain forces, which means they aren’t as neutral under acceleration as Horst-link, four-bar bikes, dw-link, or Split Pivot bikes. However, when brakes are mounted on the seat stays, dw-link, Split Pivot and FSR four-link bikes have an advantage while braking over rough ground.[4] One manufacturer well known for their long-time use of the seat-stay pivot four-bar link suspension is Kona, who incorporate the design on their entire line-up, along with other manufacturers such as Infiza and Icon.