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This is a medium sized Men's Heavyweight shirt. I normally wear a large. I purchased this size to get a tighter fit which seems more appropriate for bicycle riding.
You can find the measurements for this shirt here. Just scroll down a bit.
To give you an idea of how I fit in this medium sized shirt my measurements are: 71" (180 cm) height, 60.6" (154 cm) shoulder height, 40.2" (102 cm) chest, 37.4" (95 cm) waist, 40.6 (103 cm) hips.
Here is a picture of the small sized bamboo shirt (again I normally wear a large shirt):
You can see that the shirt is shorter, but still fits well. These is after three washings. The bamboo shirt is more expensive but it is very soft and feels great. You can compare the measurements of the shirt above and the one for the bamboo shirt to get an idea of the comparative differences (check out the links here). That's what I did before I decided to purchased the small sized bamboo shirt.