The Molten BG4000 and Molten BG4500 are both high-quality basketballs, but they have some key differences: 1. Material: The Molten BG4000 is made of composite leather, while the Molten BG4500 is made of synthetic leather. 2. Design: The Molten BG4000 has a unique pebble pattern that provides a good grip and control, while the Molten BG4500 has a traditional pebble design. 3. Intended Use: The Molten BG4000 is designed for both indoor and outdoor use, while the Molten BG4500 is primarily designed for indoor use but can also be used outdoors. 4. FIBA Approval: The Molten BG4500 is the official game ball of FIBA and has been used in all FIBA competitions since 2010, while the Molten BG4000 is not officially approved by FIBA. 5. Price: The Molten BG4000 is generally less expensive than the Molten BG4500.