Robbins
Sigma Sensitive Relay
41RZ-91558 120 Volts
This is the Sigma Sensitive Relay.
They are the one with the 5 Pins on
the bottom of them that plug in.
This is the Relay that is operated
by the Thermostats. When these
start going bad, the insulation
breaks down and they use
more MilliAmpres to operate,
thus causing a heavier load on the
Thermostat Contacts. Its the heavier
load that make them to go bad.

Some of them have a Plastic Case
and some of them a metal case.
Both are the Great Quality
you expect from Sigma.
The Sigma Relay Co. is
now out of business.