Originally Posted by unterhausen

With the SK, the early runs were sized incorrectly, but they fixed it later. The SK I have on the front of my gravel bike is marked 38mm, but it's the same size as the 43mm current production. I don't think the variation can be fully explained by tread depth either. But I think they are fairly true to size nowadays after they were browbeaten into getting out some calipers and measuring their tires.