I tested the K2Tog-L with different fibers and yarn constructions, to make sure that it looked good in other yarns apart from plied wool.
Here's the gallery of swatches.
Acrylic
Swatch made with 100% acrylic: DY Choice Baby Joy DK.
Cotton
Swatch made with 100% Cotton: Rowan DK Handknit Cotton.
Non-Superwash Wool
Swatch made with 100% Wool: New Lanark Pure Wool DK.
Single Ply Wool
Swatch made with 100% Wool: Sublime Yarns Natural Aran.
Superwash Merino, S-on-S yarn construction
Swatch made with 100% Superwash Merino: Debbie Bliss Rialto DK.