This training book has been developed from the ground up for beginners who know little about Airsoft GBB technology. As part of our Airsoft Technology Self-Paced Training Series, this book is for those who want to assemble and maintain their own GBB gearbox. Simply put, this book is for starters who want to maintain and repair GBB gearbox on their own. Step by step photos and instructions are provided to make sure all concepts and methods are clear and precise. The WE GBB model is used for demonstration here.