yes it will fit your canon xt and it is a Canon Brand Lens, USM is the more quick focus, if you have any more questions, let me know, o and if you want to pay a little bit more i'll throw in a circular polarizer, 8 point Star filter and a Diffusion filter. I'd want about 210 with all of that.
Canon Lens: 250
Canon hood: 25
UV: 10
CPL: 15
8pt Star: 15
Diffusion: 15
total: 330 + tax

so it is still an excellent deal