practically, in modern milliliter to liter-scale laboratory operations involving condensers, pieces of apparatus are often held together tightly by complementary, tapered inner and outer joints ground to produce very tight fits (augmented as necessary by ptfe rings or sleeves), or uniquely formulated greases or waxes; increasingly, other means of joint glass, such as threaded fittings with adapters, are used, some of which are also used across the range of process scales.