"THC" sensors have an attached waterproof probe on 10' cable ideal for monitoring hot tubs, pools or freezers. Wireless for ease of set-up and transmit environmental data via radio waves. Compatible with BA928, BAR338PA, BAR888, EMR812, JMR838WFA, JTR168LR, MTR101, RMR112, and RMR166. Actual Size (2 3/4" x 3/4" x 4")