One reed petal is NOT enough!
 
Boyesen's revolutionary dual-stage reed design delivers more usable power than stock. Stock single-stage reeds operate most effectively within a relatively narrow RPM range and are limited because of the single stage design. Boyesen's one soft reed on top of one firm flow-through reed gives you a wide range of intake control, plus increased intake velocity. Your original reeds can't possibly duplicate that performance. The dual-stage design allows you to replace your stock reed stop with a Rev-Plate which permits the reeds to open freely and function efficiently. 
 
Fits all models of Montesa 315 1960 - 2004