This lid is the same lid we include with our 15G - 42G conical fermentors. This thing is heavy duty and has one 3" and two 1.5" Tri Clover Compatible ports.
The 3" port is great for dry hopping. Recently people have been adding a sight glass to one of the ports to purge the hops before dumping them in. This helps reduce oxidation in the finished product. Having two 1.5" ports means you have options for what you want to add to the lid. A good setup might include a PRV for pressuring the tank and a barb for a blow-off. By using standard TC ports on the lid it gives you the freedom to customize these however you want.
Converting a sanke keg to a fermentor? This lid is perfect for you. Weld on an 8" ferrule to the top of a sanke keg combined with this lid and you have yourself a great fermentor.