Birdsall Marine spreader light clamp assembly is designed to allow you to add a spreader light to your T-top, without having to weld on a mount. It is offered in 4 different sizes depending what pipe size you have on your T-top.
Note: To determine the outside diameter. Measure the circumference. A simple and accurate way of doing this, is to take a piece of string and wrap it around your pipe. Measure the string length and divide the length by 3.14 = Outside Diameter