Sorry, not sure if I understand the question. Basically, if you have good solid T-Mobile coverage in your area that never roams, and you don't travel much, you'll probably be fine with any phone you choose. But, if you ever go into roaming in your area, or if you travel a lot, you might want to consider a phone with the GSM 850mhz band.

how far of roaming?

Yes, a tri-band phone will work with T-Mobile, regardless of whether it's US, European, Asian or whatever. Keep in mind though, if the phone you choose is lacking the GSM 850mhz band, you will have limited roaming coverage (possibly none at all, it depends on T-Mobile's roaming partners in your area and which band they use).

i have t mobile

Beware of scammers, I just deleted a scammer's post from your thread.

If it's a USA tri-band, it'll work fine. If it's a European/Asian tri-band, depends on who your provider is... so give us a little more info... thanks.

I was womdering how good a tri-band phone will work in st louis missouri?