This is a copper jumper strap normally used with the ground wires in the spa. These are mounted on the back of the pumps connecting the ground wire. Is part of the connections from the heater to the PC Board.
The sensor assembly is specifically designed to go with Down East Spas and Legend Series Master Spas (select 1996-1999 models). It is a replacement for Balboa Dual Sensor Assembly with Temperature and Hi-Limit Sensor. Compatible with all Balboa systems that use this type of sensor.