Quote from Duncan racing ....
(Unique 4-Sided design offers a power gain at all RPM ranges.
Install the Pyramid Reed Valve and your engine will have better throttle response, stronger midrange and increased top end power.
Why does the Pyramid work so well? Side pedals distinctive to this design open easy at low RPM's giving engine better throttle and more low end. As RPM's climb through the powerband reed pedals on all 4 sides open giving the engine MAXIMUM flow making better power in the mid and high RPM's.
Recommended Applications: Works Great in all riding conditions, with stock or modified engines.
The #1 ATV 2-Stroke Reed Cage.
Works best with stock OEM Intake Manifold
It is not recommended to use the Pyramid Reed Valve with any type of reed spacer.)
They sell for $175 new. You can buy the replacement reeds for $39.00. So i would say if theY go for as cheap as it looks like they might, they should be worth it.