Size is enlarged by using a larger needle.
Needles and gauge given above are for the S/M size. The L size requires a US 13 / 9.0 mm needle and a gauge of 10 st and 14 rows = 4” in stockinette stitch.

Like some other loop-d-loop pieces, this vest was originally developed for boutique production with these criteria in mind: It must be obviously hand-knit with prominent full-fashioning marks, be quick to knit by hand but a pain to do on a factory machine, look modern yet nod to fashion history, be rustic yet clean in styling, and emphasize the lines of the female form. The shaping in the front and back of the bodice, an exercise in aligning paired decreases and increases, creates a directional hourglass in the fabric. It is reminiscent of the triangular corseted bodice worn above a farthingale, the bell-shaped hoopskirt of the Elizabethan era. I can also imagine this vest in a space-age color for a techno, sci-fi look.

-- description from Loop-d-Loop, pgs. 26 50 (pattern on pg. 50)