Size does matter

I purchased an Under Armour compression tee at a local store in a size Large. The shirt fit fantastic. I wanted a back up so I purchased this one online size Large, different color. The shirt arrives on time, open the package and it is a Large but does not even fit over my shoulders.... I contacted the vendor for an exchange. They do not do exchanges but will allow me to return the shirt. If the shirt was worn it has to be washed before returning it... no problem for I could not get the shirt on anyway so tags etc were all in place. If you pass 30 days, there is a restocking fee of 20% which I was unaware of.When I questioned the vendor why I have a Large and ordered the same size it did not fit. The vendor stated that Under Armour has different sizing charts for different shirts. That just did not make sense. How are you to buy a product with "floating" sizes.So, I went online to Nordstrum to find the same exact heat guard compression tee. There was a size chart that could be pulled up to check size before ordering.... only 1 chart for Under Armour. I did all the measurements correctly to find that I was to order a Large.I know the shirt fits tight but since I already HAD a large that fits, and the chart from Under Armor at Nordstrum confirmed that I had ordered the correct shirt size, the statement that there are different size charts for different Under Armour shirts " just doesn't fit!".I personally will visit a store and actually try it on to avoid the hassle and disappointment of waiting for a product that does not fit, seemingly was ordered correctly, and then had to be mailed back.