Product Description
Rare first generation of the Simplex Demultiplicator, model #2343. This one is all metal, with the old Simplex "S" logo engraved lightly on the band. The 70's version of this was similar but had the bolder Simplex star logo, and #3637-L later 1970's and early 1980's had a derlin plastic cable tunnel and a thin band that said Simplex.
This gizmo is used (primarily) with friction bar end shifters to make the rear shifter less "sensitive" to input and easier to shift smoothly. It changes the shift ratio to allow for bigger lever movements per shift. The left side is a simple cable stop for your front derailleur. It was also recommended for tandems.
Condition
New old stock, no package