From the product description, check product page for current description, price and availability:

This stainless cooling coil is 4″ wide and 27″ long, and fits a variety of fermenters, including the Fermzilla by KegLand. Note that you will need to cut the pipes with a tubing cutter to get it to fit the smaller 27 liter Fermzilla. The hole diameter needed for the tubing bulkheads is 7/8″ or 22mm. These holes can be easily cut with our Step Drill, item C67.

The stainless tubing itself is 9.8mm (.37″) in diameter, and Duotight bulkheads are included to attach the pipes to your fermenter lid. You can also attach 3/8″ tubing with hose clamps if desired to the tubing ends to run your cooling or heating water.