Provided is a compressed natural gas (CNG) fuel system that can include a frame and at least one container. The frame can include a first side and a second side, with each side being configured to partly define a portion of an interior space. The at least one container can be configured to house or contain CNG and can be engaged to and partly encased by the frame. The at least one container can be partly located within the interior space of at least one of the first side or the second side. The frame assembly can be engaged to a chassis of a vehicle such that the at least one container is located either at least partially underneath a cab of the vehicle or at least partially behind a cab of the vehicle.