The Swim Secure Bum Bag is a must for any swimmer wanting to keep their belongings safe. It is bright and is recommended for open water swimmers, equally it is great for use whilst running and taking part in triathlons. It includes a waist strap, and triple seal pocket. Size 21.5cm x 15cm flat and empty The adjustable belt design clips securely around the swimmer's waist, and is very low drag (you generally don't notice it is there).