so i bought both a short sleeve and long sleeve base layer from Core Merino. Big shout out to them, i got my size selection wrong and the service from them was excellent, replacement arrived a few days later and all i needed to do was return the garment to the same courier, no extra cost. Cant comment on longevity but i have already used the sleeveless baselayer multiple times and it is really nice. Just watch the sizing, especially if you are used to European cycling clothes sizing. As an example, the long sleeve i bought from them was medium and had to be returned for a small. I have a Rapha merino base layer that is a large and it is exactly the same size as the Core Merino small.
