Don't think you'll have to, the sleeve goes into the hub to reduce it from 15 to 12 and all you'll need then is a 12mm bolt through/QR to fit the forks.
Some forks with 12mm through have a surround on the dropout so 15mm hubs don’t fit... super annoying!
Ah, good to know! File that down? ;)
@sbbohr started
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Don't think you'll have to, the sleeve goes into the hub to reduce it from 15 to 12 and all you'll need then is a 12mm bolt through/QR to fit the forks.