I tried Cellucor C4 Ultimate and was disappointed from how little pump it produced and it being too stimulating (300 mg caffeine) which gave me headaches. I tried Mutant Pump as a stimulant-free option instead. It's the best pump I've had since forever. My muscles felt full and pressurized without flexing. It worked shockingly well. If you want to enhance your pump, this is absolutely the supp to get. It's a capsule, so taste isn't really a factor. Drink LOTS of water. I went through 2+ liters over the course of a 90 minute workout.