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. 4-40 are for use with.093 dia rods spring keepers are 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. 4-40 are for use with.093 dia rods spring keepers are included. Weight per link: #109 #600 #112 & #305 - 1 gram/link #304 #601 #603 & #604 - 1.5 grams/link.