I've used the ones from bargain fittings on my keggle and MLT. They work fine, no leaks so far. If you use a step drill, you can easily make the proper-sized hole. I placed mine as low on the vessel as I could while still being able to attach the fitting inside. I only have about 350 ml of deadspace in my keggle. The fittings, in particular the o-rings, conform to the rounded shape and seal everything up.