90604-ZY3-020 Tube (D21) Clamp - Overview. The 90604-ZY3-020 Tube (D21) Clamp is a crucial component designed for Honda marine engine systems. This clamp supports the marine rigging and accessory system by securely fastening the D21 tube, ensuring reliability and seamless integration within Honda marine equipment. Designed to meet factory specifications, it maintains the structural integrity and durability of the marine system it supports.. Key Features. Serves as a high-quality clamp for the D2