Experience may vary person to person, but I was able to specify collar length, width and shape, arm length, body length, and general diameter. Specifying higher armholes, smaller sleeves, larger cuffs, or changes to body shape beyond general diameter were turned down as "this is not grand-mesure, sorry we don't do that on demi-mesure." My saleswoman was very friendly and helpful, but the demi-mesure experience was quite limited for me. This is more than they'll let you do at Bergdorf. You can't pick the length of the collar points and you're stuck to stock body sizes within a certain range of your neck size. I don't know unless you are talking about changes to a stock collar as opposed to picking a particular collar, this sounds exactly like what I do at Bergdorf. Pick the fabric, collar, and cuff, they measure your arm and then you can request slight changes to the body length and diameter. The collar selections on display are limited, but they'll order whatever collar you want (if you know which one you want). Of course, fabric selection is just a fraction of Paris. Nice order by the way. Also, M. Colban is supposed to be coming in March with new swatches.