Air Vent Screw for Rotax Max Evo Engines. This crankcase vent is a threaded plastic, and allows for excess crankcase pressure and oil to purge from the system during engine operation.
Note that this screw is a 'thumb' type screw, and is intended to purge oil from the gear case of the engine (although it technically threads into the crankcase body).
This is also part 30 for the DD2 crankcase.
Each vent screw is M18 x 1.5 thread.