Proudly Made in the USA, the Rectangular Current Transformer Model RT3737 was designed to fit over bus bars and to be fully encapsulated for indoor and outdoor applications. It's rectangular design with a window diameter of 3.75 x 3.75 and a standard 1-amp secondary. Others available. The RT3737 terminals are brass number 10-32 UNC with one flatwasher and lockwasher. CSA Optional. This model weighs in at approximately 2lbs.