Eek, look is the sale price is $35 or so dollars then that bag only cost them about $15 to $20 wholesale which means it's made very poorly. If you want something like that then look at Camelbak bags, they are the leader in that area and they build high quality bags, water bladder, and mouth pieces; sure it won't be as cheap as the one you're looking at but it will last at least 5 times longer, plus if the bladder goes bad you can buy just the bladder. My Camelbak is about 20 years old and I still use the original bladder. My Camelbak was called the Rogue, which they still make but mine only held 70 ounces, which was fine with me because I didn't want a lot of water weight on my and back and I carried 3 bottles on my bike as well, the new Rogue holds 85 ounces. They still make my 70 ounce bladder because they have a 70 ounce version of my bag now as a woman's bag.
The smaller 50 ounce bags cost $50, and the larger 85 ounce bags cost $70, I would go with the 85 one, if the weight of the 85 ounces of water is a little bit more than you like on your back simply reduce the amount of water you put in, but you will always have the option to put more in.