100% Polyester, it is suitable for summer and spring wear. this is a great gift for your puppy.
Please measure length,neck,and chest of your pet, It is better to choose the shirt size based on the chest of your pet,The measurement chart is as following:
Small: Back Length 9.4", Chest Girth 14.5", Neck 9.8"
Medium: Back Length 11.4", Chest Girth 16.9", Neck 11.8"
Large: Back Length 13.4" ,Chest Girth 18.9", Neck 13.8"
X-Large: Back Length 15.7", Chest Girth 20.5", Neck 15.7"