TIRE suggestions for son new raptor 250

[337450r]

I am wanting to order new tires for his new to us 250, they come with a oddball size, what is everyone using/size, it will be for trails only

[337450r]

What about these,

http://www.motosport.com/atv/2008-yamaha-RAPTOR-250--artrax-mxt-front-atv-tire-21x710?mmy_source=pdp

If I did these in 21 7 10, would it fit stock rims on the front and would I also need to go up a size in the rear?????