Authentic Hockey Jersey Sizing

What should I know to buy a jersey of the NHL for my boyfriend?
I am in the process of buying my friend a jersey Pittsburgh Penguins for Christmas. However, I have no idea where I should do or what you are looking for. I do not want to be wrong or pulled. He plays hockey, but I doubt he will play on it for fear of ruining it. In addition, he is 5'10 175 lbs. Money is a problem. So basically I wonder: Where should I buy? Authentic or replicas of what size? What do you think about buying from here http://pittsburgh.craigslist.org/spo/1494773957.html Other suggestions? All information will be greatly appreciated. thank you sooo much!
I recommend a fan of Pittsburgh. If you live in Pittsburgh, have a shop on the street from PNC Park, however, you can find online as well. It www.ThePittsburghFan.com have a sale for the holiday season, so most of their shirts are less ones that you will not find anywhere else at this time. I bought them before and never been disappointed with the quality, price or speed of delivery. authentic are much better, but obviously a little more expensive. I know you said that money is a problem, but if the price is not true outside of your price range, I'd say spend the extra money. You will not regret. For its size, I would certainly great. Given the height of her boyfriend and weight, which must fit perfectly. Buy Craig's List is not always bad, but the link is always a bit superficial. I recommend buying an officially licensed dealer. Here is a link to Penguins Jerseys few: http://www.thepittsburghfan.com/Pittsburgh-Penguins_2/Jerseys_15/?leadsource=CAM29357 Hope this helps! Great gift idea!