My 6th design of an intake hose for the old two-stroke Aprilia RS 125.
It has funnels for air intake and it takes in consideration that the overall length has to be longer when having larger corss-section according to helmholz resonance frequency formula.
The intake part is bent downwards because otherwise there would be no space due to the fuel tank.
It is designed to be printed with flexible filament (TPU) and can't be mounted when using PLA or other stiff materials. The inner flap is smaller than the outer one so it is easier to push inside the airbox than the original intake hose. There is no need to disassemble the airbox.
Photos show a previous version in an old MP model, this one already has some improvements (one side is longer on the outside)