Yes, custom ute trays can be designed and built to fit specific vehicle models and meet individual needs. The length options you mentioned, 1600, 1800, and 2100, are common sizes for different types of dual-cab vehicles. The 1600-length is suitable for most dual-cabs, but only offered for Tritons. The 1800-length is suitable for most dual-cabs and the 2100-length is ideal for extra/space cabs.