This is the 17.5 degree long 5th gear with "X" marking for models built after 04/1982.

Simply replaces the original gear wheel and results in approximately 5% taller gearing. This enhancement will increase your top end speed but also improve your fuel economy at normal traveling speeds. 

Two versions of this part are available!

Starting 04/1982 BMW made a change to the gear angles in the 5 Speed gear box. The gears in the early gearboxes were machined at a 15 degree angle. From 04/1982 the gears were machined at a 17.5 degree and these were marked with an "X" on the output shaft gear. Unless you know the entire history of your bike, you should probably see what's inside before ordering.

The available versions are:

15 degree (without "X") before 04/82 production (See part number GEA22889)
17.5 degree (with "X") after 04/82 production (THIS PART)

This part is not even available from BMW!

Made in Germany.