HEAD Marlin/Volo One Snorkel and Fin Set gives you everything that you need for your next snorkel adventure with this package, which features a Marlin Purge Mask, a Marlin Dry Snorkel and Volo One fins in a travel-friendly backpack. Small/Medium fits shoe size US 3 1/2 - 6 Medium/Large fits shoe size US 6 1/2 - 9 Large/X-Large fits shoe size US 9 1/2 - 12