With the same features and benefits as the Intermediate Speed Bag, the Professional Speed Bag offers more challenging weight resistance. This model is designed for those who have experience with lifting weights or for those in advanced martial arts and other upper body sports. It is 12 lbs. in weight, but its not the weight so much that offers the workout, but it is the mechanics of the workout. This model offers the buyer a very challenging and unique workout. Not only does it incorporate all of the upper body and core strengthening attributes of the lighter model, but the added weight also creates a heightened aerobic and recruiting type workout which is much more challenging to the average person. A recruiting type of workout means calling on all aspects of core strength, agility, and aerobic muscle groups, as well as a keen sense of coordination and endurance. This machine is for those who are serious about getting to the next level in any level of fitness. It is the next step up after mastering the 8 lb. Burn Machine, which is excellent to switch to when lighter training is needed.