The only pyrex cup gas lenses that are worth it are the super wide mouth gas saver. Still the pyrex cups are very fragile, so you have to be very careful where you lay the torch down, and the glass gets very hot.
I use the super wide mouth for very fine stainless steel and titanium joints. It was designed for Boeing to use on Titanium.
CK is by far my favorite TIG torch company. It doesn't hurt that I can drive to their shop and pick up a will call order, or get a new custom torch the same day at most Seattle area welding suppliers.
They are based in Auburn, Washington, across the street from Tec Welding Sales.