The Wechselapparat M.1917 (Wex) was a World War I German flamethrower introduced in early May of 1917 to replace the earlier Kleif.

It was developed by engineer workshops within the Guards Reserve Pioneer Regiment (Garde-Reserve-Pionier-Regiment), which was the main flamethrower unit of the Imperial German Army.

The Wex was deployed in a group of four: two operators (one to carry the tank and the other to wield the lance), one officer, and a grenadier.

Some Wex flamethrowers survived the Revolution despite the Treaty of Versailles and have been used by the Finnish and the Polish armies in the 1920s.

The doughnut-shaped container design was copied by the British during World War II as the Flamethrower, Portable, No 2.