Created by a PhD Dietitian and ultra runner, Spring is fuel created out of natural foods. It is designed for optimal gut absorption to prevent GI problems and blood sugar dips. Recommended use is every 30-40 minutes during exercise lasting more than 1.5 hours, and the SpedNUTgel is great if you're really pushing (250 calories and contains some fat!) Other flavors range from 100-180 calories, and Hill Aid contains 41 g of caffeine, almost a half cup of coffee