MCS-578380 - Used in custom applications to reduce exhaust sensor thread from 18mm to 12mm so late H-D models; equipped with 12mm O2 sensors; can be used with earlier 18mm sensor style exhausts. Note: For Touring models an extra extension cable is required; which is

Fitment:
12-17 Softail; Dyna (with pre-2012 exhaust) (NU); Other applications were 12mm sensors are used for 18mm holes