As I tried to indicate in my "also" note above, not all russians are alike. The male I mentioned was purchased at about 4.25" and maybe 400 grams. After 2-3 years he had grown less than a quarter inch and reached maybe 425 grams, which I attribute to the growth-inducing wonders of the captive environment, not to him being immature. He was weathered looking and had the appearance of age.

There are supposedly subspecies, and I would imagine a variety of potential sizes. I doubt that that 4.25" male, who now lives elsewhere, would ever reach 5". The largest tortoises I have are about 6.25" and 7" and show no signs of reaching the 8" that others report.

So don't discount the breeding potential of your tortoises.