Notes on sizing from Elann.com:

One size to fit most women (S, M, L). Only the placement and the length of the armholes are actually “sized”. The vest is a circle, knit in 8 equal sections, with armholes made in sections 2 and 7. The sample garment was knit to 9.5” from the center of the circle, at the point where its armholes measured approx. 10” in length. For smaller bodies, armholes can be made sooner than this, which will result in a smaller garment and a shorter armhole length. For larger bodies, continue knitting past 9.5”, until 2 sections measure the desired width across back, and armholes are desired length. This can easily by determined by placing all stitches on a length of ribbon, and placing the knitted circle against the back of the intended wearer.

To calculate yarn requirements for larger or smaller sizes, determine desired back width, and compare it to sample garment’s back width as a percentage, and then increase or decrease your yarn requirements by this percentage – e.g. sample garment’s 19” back width used 9 balls, so a 21” back would use 10 balls (21 divided by 19 = 1.1, and 9 x 1.1 = 10).

Formerly available at http://www.elann.com/ShowFreePattern.asp?Id=254024.