Includes:
Springer fork disc brake bracket, chrome 505216
Adapter, CNC polished  505215
Disc brake rotor size 160mm  505217

Front hand brake lever  505208
65" bicycle brake cable  505212
Disc brake caliper for 160mm rotor  505203

Application
Ad a disc brake to a springer fork - video
Works on 20" and 26" bent or straight springer forks

Thread the adapter 505215 onto a free wheel; bolt 160mm rotor 505217 to the adapter with the 6 screws; place the wheel on the left fork leg with the caliper.  
Important instructions (warning): Use thread locking glue between the hub and adapter and all other screws included. Use Loctite Threadlocker Red 271 High Strength, or equivalent glue.