If you're really worried, you can take a shirt that fits comfortably, and measure the same dimensions that gemini shows on their site and compare. I normally wear XL in polos, and i have a XL gemini jersey that fits "ok"....i also have a couple XL high 5 gear jerseys. The fit of the High 5 Gear jerseys seem truer than the gemini jersey and fits very comfortably. I also prefer the material of the High 5 Gear jerseys....as well as the price...lol
Either way, good luck!