I use these fittings to vent 15-gallon kegs of white wine that I ferment in a freezer. I connect the fitting to an airlock to vent CO2 during fermentation. I also initially had problems with them breaking when I tightened the connection to a SS lid (similar to the fitting on this cellar keg https://morewinemaking.com/products/morewine-cellar-keg-50-liters.html but w/o the racking tube.). I found that by using the gray Teflon tape (which is thicker than the white) and wrapping the threads several times the seal could be easily made w/o overtightening the fitting.

Works why cant there be a stainless alternative for this? They easily break.

Thanks to the previous reviewer I was quite conscientious of my tightening. A little teflon tape and some care when tightening and no problems. Time will tell how the plastic ages.