Raleigh made 2 types of Twenty; one with 451 rim size and the other bmx rim size. I think the only difference between the two (besides the rims) are the brakes. the bmx size have longer reach brake arms while 451 have the regular brake arms. I've seen both size of twenty side by side and as far I can tell the forks were the same. If you are going to use the stock fork then 451 should fit and get your self a pair of new Caliper brake and you'll be on your way.