I had to start with 6 in., no choice. 33 is my pant inseam size but with the boots on it hovers around 34. I have the " 0 " now and am as happy as I can get. I would go with the 4 in. and I'll tell you why. There are a bunch of 6 in. extensions out there sitting on shelf's because back then everyone had to start with 6 in. If you don't like the 4 in. you could probably swap with one of the shelved 6 in. If you get the 6 in. and don't like it, it will be sitting on your shelf also.Yes, they offer 0, 4" and 6". My 31" is my pants inseam.