What is the Physio Room.com Instant Heat Pack? A mouldable pack that becomes an instant therapeutic heat pack. Ideal for soothing warm pain relief. Single use only. When can I use it? Instant Heat Packs are ideal to be used in the treatment of pain & muscle spasm, in circumstances where you dont have access to an external heat source. Ideal for applications such as neck pain, arthritis, back injuries & shoulder injuries. Instant Heat Packs can be carried on day trips & away matches where conventional hot packs are not practical. Size Measures 16cm x 23cm (6" x 9") approx. How does it work? Instant Hot Packs are activated by squeezing an internal compartment within the pack. This starts a chemical reaction that instantly makes the pack warm. The Instant Hot Pack stays warm for 15 to 20 minutes. Single use only. Always follow the instructions.