Analytical balances are a type of dedicated scales, designed for weighing extremely small, light objects.
These balances are typically required to measure weights in the sub-milligram range (lighter than 0.001 grams).
As these balances are tasked with working with extremely small margins of error, it is vital to minimise the risk of contaminants affecting the accuracy of the final measurement.
To help facilitate this, analytical balances often feature preventative features such as glass enclosures which help to keep dust and other materials from entering the measuring area.
These glass walls (often referred to as 'draft shields') also help to prevent air currents inside the laboratory from hindering the accuracy of the balance.