The phrase "are a normal feature of" is correct and usable in written English.
It can be used to describe something that is commonly found or typically occurs in a particular context or situation.
Example: "In urban areas, traffic jams are a normal feature of daily commutes."
Alternatives: "are a common aspect of" or "are a typical characteristic of".
Delays of many hours or even days are a normal feature of a trip with Amtrak.
Mosques are a normal feature of our cities, though they are yet to be seen as typically Australian.
Production slowdowns are a normal feature of the auto industry in mature markets like the United States and Japan, where inventories are kept from ballooning, keeping pressure off automakers that would push them into offering discounts, at a cost in profitability.
Kinetochores associated with individual chromatids are not a normal feature of meiosis I, but they are a normal feature of mitosis.
We therefore conclude that the sphaeroplast structures observed are a normal feature of HI morphology, possibly sometimes caused by damage and not (or at least undetectably rarely) the result of cannibalism.
The situation was similar in Asia, where urban and rural penury was a normal feature of economic life; moreover, the decade of the 1930s is forever linked to the spread and brutality of Japanese imperialism.
Interestingly, the Treasury Department does not include Medicare on its list of tax expenditures, because it considers this to be a normal feature of the tax system rather than an exception, but Congress's Joint Committee on Taxation does.
They also support the notion of changing patterns of behavior being a normal feature of early development.
The difference is that virtually everyone seeks to avoid a collision, while deception is a normal feature of ordinary linguistic interaction.
A dependence of τeff on the initial temperature (at constant δ) is a normal feature of linear and nonlinear systems with wide distributions of relaxation times.
