Du-Bro 2-56 Spring Steel & Solder Kwik-Links Part No: 109. Spring Steel Kwik-Links are the tried and true top quality Kwik-Link. Ideal for control linkage hook-up. Use with threaded rods or threaded couplers. 2-56 are for use with .072 dia rods, link guards included. Solder Kwik-Links are nickel plated making a strong, attractive and easy to solder connector for servo or control horn. 2-56 Solder Kwik-Link designed for use with .072 diameter rods, link guards included.