The T2125M upgrade from GSR2 to GSR/Temp2X is for people who already have a GSR2.
The GSR2 upgrade kit includes all the products in the GSR/Temp2X except the GSR2 device itself. It is designed for people have the GSR2 and want the additional flexibility and benefits of the GSR/Temp2X accessories.
The GSR2/Temp2X includes a temperature sensor for monitoring heat levels in extremities. Stress also reduces blood flow to the hands, causing cooling.
The GSR/Temp 2X home biofeedback system allows you to do "hand warming" biofeedback in addition to training with the GSR2 monitor, temperature sensor, body sensors for hands-free use, dual-sensitivity meter, earphone, instruction manual and a CD with a short relaxation program.