Health Fitness GXN Mass Gainer| Rapid Gain Mass Gainer| 376 kcal & 19.5 g – Shop Now nutritiongxn0091 356 views GXN Rapid Gain is the perfect mass gainer to improve your metabolism and enhance the immune system, use this supplement just after the intense workout for the effective results. Shop Now at Best Price. gxn mass gainer rapid gain mass gainer