The phrase "are remarkably constant" is correct and usable in written English.
It can be used to describe something that remains stable or unchanged over time, often in a scientific or analytical context.
Example: "The results of the experiment indicate that the variables are remarkably constant across different trials."
Alternatives: "are consistently stable" or "remain notably unchanged."
In contrast to the behaviour of most oceanic substances, the concentrations of the principal inorganic constituents of the oceans are remarkably constant.
And while changes in technology, the way news is consumed and public attitudes make for an ever more challenging commercial environment, the underlying ethics of the trade are remarkably constant.
The redox potentials are remarkably constant along this series, but the peak separations increase, reflecting slower electron transfer due to more effective adsorption on the electrode.
To summarize: the transmission properties of the photoreceptor membrane are remarkably constant over the tested temperature range.
Bazin et al. [6] showed, for the first time, that levels of sequence diversity, in mitochondrial DNA, are remarkably constant across species that apparently have very different census population sizes; for example they showed that several groups of animals including mammals and molluscs, have very similar levels of mitochondrial DNA sequence diversity.
It has recently been shown that levels of diversity in mitochondrial DNA are remarkably constant across animals of diverse census population sizes and ecologies, which has led to the suggestion that the effective population of mitochondrial DNA may be relatively constant.
While vulnerable to pathological, physiological, and pharmacological stressors, cardiac rhythm control is remarkably constant and robust.
The style of costume worn throughout the Middle East has been remarkably constant for centuries.
Yet somewhat surprisingly, the rate of return on capital is remarkably constant over long periods (see chart, second panel).
One neighbor used to keep count of the children on the block at any given time, and the number was remarkably constant, at fifty or so.
The circumstances in which the art of criticism is practiced are always changing, but the state of the art is remarkably constant.
