APPROX SCALE
The filter flask in the situation of room temperature or heating, it’s easy to make scale fuzzy and incovenient to experiment. But the APPROX scale is more accurate and durable,not easy scratches
UPPER TUBULATURE
The short tube effectively act as an adapter over which the end of a thick-walled flexible hose (tubing) can be fitted to form a connection to the flask. Can be connected with a hose to source of vacuum such as an aspirator, vacuum pump.
GOOD PHYSICAL STRENGTH
The thick wall of the filter flask provides it the good strength to withstand the pressure difference while holding a vacuum inside.