THUNDERSHIRT FOR DOGS ▪︎ Size Small ▪︎ Gray Color ▪︎ Great Pre-owned Condition (package is missing closure twist tie) Stop problem barking, chewing, and anxiety in your dog the natural way with the ThunderShirt Dog Anxiety Shirt. ThunderShirt's patented anxiety jacket design applies a gentle, constant pressure that has a dramatic calming effect. Using pressure to relieve anxiety in people and animals has been a common practice for years such as swaddling infants and the use of gentle pressure and weighted vests to help people with autism.