to me the 250A/350D, ATC250ES Big Red ( 2 inches wider ) is a much better rearend , the axle tubes go all the way to the hubs and the axle being supported by bearings on the ends is a much stronger design that does a better job of sealing water and dirt out , which in turn makes it last longer ....here is my most recent 250 rear end swop , which was a surprise , my buddy came over riding two weeks ago and blew out his 96 300 Fourtrax 2wd rearend , we took it apart at my house , the axle was frozen in the splines of the ring gear and we tried for an hour to get it out , his buddy at a machine shop broke the housing while trying to get it apart in a 50 ton press , so he asked me to find him a 250 rear end and modify it for him , so to save me time and work I found a guy on e-bay that sells 250/250 rearends , rebuilt with new bearings , seals ,brakes and is welded up with mounting bracket and ready to install , with shipping for $525 , which isn't bad , on average by the time I find a rear end , weld it , do the bearings , brakes and seals I got $300 into it , not even counting any of my time ------------anyway my buddy just got a repo house and says he ain't got time to ride no more and he wants to put money on his house and not the bike , ssooooooo , he says will you give me $500 for the bike , found a rear end for $171 on e-bay but when it arrived and I took out the axle it was toast , it had been welded to a hub previously as the spline stripped out , they had cut the weld with a wide blade grinder and cut into the axle 1/3 the way around , both hubs had seal rings grooved into them and needed to be replaced , I contacted the seller Mrtoolbox and he was vey helpful , he sent me a pic of an axle and hubs in great condition and says they are on the way , the rear end is in the jig with brackets in place and just need to be welded up -----------good engine , tires and very dependable , only thing wrong with the bike is it is green and not red ----------------- here's a few pics