From Interweave Knits:

“Linda Niemeyer and Diane Zangl joined creative forces to design this sleek, color-blocked alpaca-silk pullover. They’ve chosen a twisted rib pattern to give body to the somewhat slippery yarn and to help the sweater hold its shape. A sneaky dark blue line down the sleeve--not visible when the sweater is viewed straight on--creates a long, lean look and leads the eye toward the optional thumb slit.”