The Klein Tools 54818MB MODbox Internal Rail Accessory is a dark gray tool box accessory made of hard plastic. It has dimensions of 4.1 inches in height, 17 inches in length, and 1.9 inches in width. The MODbox Internal Rail Accessory is designed to provide internal storage for tools and accessories within the MODbox tool box, allowing for organized and easy access during home improvement and workshop projects. The California Prop 65 Warning ensures users are aware of any potential health or safety risks associated with the product.