Small species like nortwesterns and butlers garters can be happy in a well decorated 10 gallon, but more space is appreciated.
Larger and more easily found species like checkered, radix and easterns will outgrow 10gal in a year or so, but are generally easier to keep.

Flames are a selected color strain of eastern garters- price depends on age, degree of color, and breeder reputation. A well bred snake with known parentage is more likely to develop the promised coloration.
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