ct:

The carat (ct) is a unit of mass equal to 200 mg (0.2 g; 0.007055 oz) and is used for measuring gemstones and pearls.
The current definition, sometimes known as the metric carat, was adopted in 1907 at the Fourth General Conference on Weights and Measures, and soon afterwards in many countries around the world.[i]
The carat is divisible into one hundred points of two milligrams each.
Other subdivisions, and slightly different mass values, have been used in the past in different locations.
In terms of diamonds, a paragon is a flawless stone of at least 100 carats (20 g).


oz:

The ounce (abbreviated oz; apothecary symbol: ℥) is a unit of mass, weight, or volume used in most British derived customary systems of measurement. The common avoirdupois ounce (approximately 28.3 g) is ​1⁄16 of a common avoirdupois pound; this is the United States customary and British imperial ounce. It is primarily used in the United States to measure packaged foods and food portions, postal items, areal density of fabric and paper, boxing gloves, and so on; but sometimes also elsewhere in the Anglosphere.