I also use an ice pack gel vest that isn’t truly ice as to not shock their system which would defeat the cooling purpose but it maintains safe temperature to assist with cooling and provide some longevity before it losses its coolness.  This design was originally created I believe for military working dogs for the desert wars the USA fought,  The biggest issue I have with GEL packs is the added weight for the dog, and the vest acting like a coat limiting some airflow, so need to be cognizant how that can affect the dog. The latest ones I have used are mesh and allow for good breathability  but still have the weight of the GEL PACKS!