The original body protectors which Tommy based this on were very good, but Tommy noticed some excess leather flaps (on the original JKD body protectors) which were prone to wear and tear and also had the potential to be fairly irritating in a sparring situation when you're trying to focus on your opponent. So, Tommy has trimmed the excess material down which gives the body protector a more snug fit and negates the irritating flaps of material.
Tommy has also spent a great deal of time making this item more tough and durable than anything else like it. Specifically, he has toughened the body protector up by replacing single stitching (as was found on the original body protectors) with extra strong double stitching throughout. He has also used the thickest and toughest leather available. If you compare these body protectors to any similar ones then you will immediately feel the difference- they are slightly heavier and the leather is thicker.
Tommy spent several months in close consultation with the factory to ensure that the body protectors were built to his precise, very high standards. In the end, the final pieces that the factory produced turned out to be EVEN STRONGER than Tommy's prototype.