Hi i just got some Maui ultra fins & i need to know out what bolts fit in them. UNF coarse & fine dont work, Metric dont work. I been to 2 bolt wholesalers & 3 hardware stores no one has anything that will fit. MUF emailed me back but didnt tell me what the thread is, just hoping i dont have to wait another week for some bolts to be sent here. Thanks, Russ.

Check the threads aren't prestripped or the brass insert isn't just misaligned. Sam.

All fin bolts are M6 I thought, sometimes when new the ferrule needs to be aligned by patience (or force !) I dont bother with the supplied soft things that come with boards - especially those from Cobra! I have a large supply now of allen head a4 m6 bolts that I found on ebay, they are brilliant, easier to do up and undo.

The barrel nut (insert in the fin) is machined with a larger tolerance in the threads than a "normal" nut so it will easily strip if you hit something, thus saving your board.. That would be my guess as to why a specialist bolt retailer reckons they don't have something that will "fit" - cos it is kinda designed to not fit properly if that makes sense. They would have measured it and thought it non standard (which it is really!) Get a fin barrel nut and a standard M6 nut and check out the wobble on the former! Your chance of getting M6 at larger hardware shops like Bunnings etc is just about nil as they do patio bolts etc, and if they do have it the staff would not know a bolt from a nut anyway Buy standard M6 - which is 6mm metric and standard pitch of 1mm (25.4tpi). Any marine shop or proper fixings place will have bucketloads of them. If it does not want to screw in, as others have said just rotate the barrel nut with a screwdriver, that's what the slot on the side of it is for

I was using the patience method for hours & then it became the force method, out with the hammer & punch ( i realy didnt wont to hammer new fins) but i should have heaps earlier. got the brass insert to move a bit & the bolts fit. Thanks for the suggestions I'm going sailing today yay.

I thought so but no, not even trying to screw a bolt in before they got sent, oh well all good now.

Tectonics Maui give you a choice of the metric or US threads when you order a fin. While the Americans can't seem to handle metric at least the company has realized that there are other different needs outside of the USA.

The rest of the world has realised conformity in thread sizes is a good thing, such as METRIC, yes it was hard to begin with but the ability to stock just one line of threads to service anything that requires a fastener is well worth it, pretty well only one country left that wont swallow it's pride and let go to change! PS look at where that is getting them

Yeh it was the brass insert not lined up perfect, thats why the bolt places could'nt find anything to fit. could'nt adjust it with a screw driver they were tight but hammer & small punch moved them around & the m6 fitted. I didnt ask for screws so thats probly why none were test fitted before sending. just used the 24 & its not that different to a normal fin.

Metric is fine for a lot of things but we have a mixture of metric and standard which gets rather confusing, metric and standard together on one vehicle?! I really don't like metric for measuring temperature. "PS look at where that is getting them" not sure at all what that means.