Pro Trucker Spring Shock Light Duty Spring for CB Radio Antenna Made from long lasting, top grade brass and each spring is about 3" in length Works especially well with 2ft "KW" & "FS" series antennas as well as the 3ft "FL" or "RP" (lighter weight) antennas. Not advised for use on large antennas over 3' Standard 3/8"-24 thread that matches most CB radio setups Upper and lower inserts are made of chrome-plated machine brass Overloaded Mobile is an authorized re-seller of Pro Trucker products