My Dad wanted something to keep his ears warm while biking on cold Wisconsin days, but he couldn’t find a hat or headband that fit under/around his bike helmet. He described what he needed and I started making stuff up. His request for more thickness/warmth in the ear flaps was easily accommodated by adding another layer of knit. The 2x2 rib makes it really stretchy so it’s easy to fit. You can use chunky yarn or two strands of worsted held together, like I did.