Has anyone used the 41mm HD 3" fork extensions I just don't get it they have a threaded hole right through the centre were the oil could leak do I need to plug them with a bolt or something  thanks

throw up a pic... I installed some lately and no issues what so ever.

Air caps?

Here is a photo i hope don't really know how to do it

Here are the ones I just fitted to the sporty.  The small hole in the top is simply a slot for a screwdriver or the like to help tighten the unit into the top of the fork tube - it is hidden by the top tree clamp once everything is bolted back up.  These ones are very solid.

Yeah fitted them to my sporty to 39mm . But 41mm you can only buy the ones pictured with a hole througth the middle and threaded I don't get what the threaded hole is for

Hey Maca,if you have the original 39mm triple clamps on your sporty the extensions won't fit as this "contraption" is designed to be fitted on some OEM 41mm set up(big twins) they slide into the recess of those smaller top triple tree fork diameter hole and gets bolted from the top clamp down.

Thanks mate makes sense