This is the 39mm skylight winder arm that is the most common one on the T25/T3/Vanagon hightop model vans.
To check if this is the correct arm for you measure the part that goes into the Skylight surround as in the picture below,
We stock both styles if you have the shorter version.
CampervanCulture.com now stocks the widest range of T25/T3/Vanagon Westfalia parts in the UK with new items being added all of the time. We hold all of our stock here in the UK for fast dispatch to the UK and around the world.