Removing factory seats in the 80 Series removes the bridge harness for the seatbelt buckle sensor. This 12 inch braided extension restores that connection to ensure the dash light functions correctly (on when unbuckled, off when buckled). For the powered driver seat. That's the left seat in US trucks and the right seat in right-hand drive trucks, and the same harness fits either one.

Manual seats already have the correct length harness.