I started with Smuckers harness, 'way back in '85-my first harness was their "Lite" line, the most basic. I now have two of those(in the russet leather, no longer listed as available in the "Lite")-they are my primary 'everyday' harness, and have gone many a mile! They both fit very well, on everything I've had them on!
I also have a black with brass fittings "Pleasure" harness, and it also fits quite well, and looks perfectly nice(it is the next step up from the "Lite".)
Finally, I have a "Deluxe" in russet with brass. It is absolutely GORGEOUS! I have never used it-got carried away and ordered it without having a cart it is suitable for use with(natural wood finish with brown/russet trim), so it is for sale.
Smuckers is a well-regarded maker, and the product is clearly of quality. I have never had an issue with fit on any of my Smuckers harness, and would recommend it to anyone. Their "top of the line" harnesses compare with about any, from what I've seen and heard! Now, they also work in synthetic(beta); the photos of the beta harness look VERY handsome-and it is somewhat less expensive than leather.