[MyFairLacy]

That tank is by LuLu Pink and that brand runs about a size smaller than other brands (ie. A Medium in LuLu Pink is a Small in a lot of other brands). Lacy has that tank in a size Medium. She is a little over 7lbs, she has a 9in neck, 14.5in chest, and a 10in length. Lacy has a longer, leaner body. The shirt is very fitted in her - tight but not too tight. The first picture is of her in the tank so you can see how it fits on her. The second picture is of my boss's yorkie, Taffy, who is 3.8lbs. She is also has a thin little body. She looks good in an XS or a Small. The shirt she is wearing in the picture is an XS. It fits her well but like I said she is very little around. The last picture is of Taffy's sister, Layla, who is also 3.8lbs but has thicker hair. The shirt Layla has on isn't the same one but is by the same brand and is a small. The XS is really for a very tiny little dog. The Small I would say would be good for a 3.5-5lb dog. If over 5lbs I would go with a medium. The Large is quite a bit bigger than the medium - too big around for Lacy. I hope that helps