The new Softail® inverted forks utilizes a unique inner fork nut (Castlenut) to secure and compress the fork spring. This one-piece solid steel socket is designed to help the technician by securing the socket to the joint rod prior to final assembly.
M8 Softail with Inverted forks (i.e. FXDR, Sport Glide, Fat Bob, Low Rider S
V-Rod (Most 2012-2017)
Some Sportster models with Inverted forks