The Bodycool Hybrid 2 in 1 cooling vest is created for multiple sport purposes & commonly used as pre-post cooling vest by athletes. Hybrid 2 in 1 cooling solution for ultimate relief: Evaporative INUTEQ-H2O® Cooling Fabric for 2-8 hours of cooling relief per soaking & INUTEQ-PAC® bio-based Phase Change Material inserts maintain a comfortable constant temperature for up to 2.5 hours (depends, using the 6.5° C or 15° C inserts). Vest only, please order the optional INUTEQ-PAC® bio-based PCM cooling inserts separately. Features Incorporates a unique cooling technology Machine washable & has antibacterial properties Easy to use & re-use Lightweight, non-toxic & durable CE marked Activation Activation is easy: for the INUTEQ-H2O function just soak in water for max. 2 minutes & gently squeeze out excess water. Your vest is now ready to wear, instantly creating evaporative cooling for up to 8 hours, depending on the ambient temperature, humidity & airflow. Soak in water Gently squeeze out excess water Enjoy immediate cooling Easily integratable bio-based PCM cooling packs (to order seperately) Cool the pack Inserts into garment pockets Enjoy constant cooling Activation: simply put the product in ice water, refrigerator or freezer or store it at a lower temperature until it becomes fully solid. Cooling duration: up to 2.5 hours, depending which PCM inserts you select. Sizing T-shirt size = cooling vest size Just take your T-shirt size as a reference to determine your cooling vest size