I have the Mandrus Rotec Wheels w/ 10mm spacers on the back, and my lug bolt locks are "Cone Seat" 58.4mm overall length and 33mm shank length. I used Gorilla brand #47015-N-20 (chrome). For your 20mm spacers I would say if you went with the Gorilla brand, then you'd need #47013 N-20(if you wanted them in the chrome). Those are 40.6mm shank length, and 67.6mm overall length. BUT, please do your own homework. Not sure what brand of lug bolts you're looking to get, but the length I've suggested are within the desired # of threads into the hub w/o going too far and encroaching the emerg. brake(with my wheels).