There are atleast two variants of Echinododus tenellus. One has leaves which are approximately 1/8" (5mm) wide. The leaf length of this chain sword can range from 3-4 inches to over 10" tall; the longer leaves can occur with lower light and more crowded conditions. The other variant has narrower leaves ~1/16" (~2mm) and typically stays short (1-3"). But it can also grow a bit taller. Under bright light the leaves of the "micro" variety may turn reddish.
In the literature, both have been called pygmy chain sword plants. About 10 years ago, the smaller one was called E.tenellus var. tenellus. Now they are all generally lumped into the single species of E. tenellus.
You will also see a picture of "Veronica" sword. This plant developed by a hobbyist in the Ukraine was sent to me in 1998 by his friend, Alexei Bednii of Moldovia. Years later it found its way to Tropica (thru Karen Randall) and it is now sold under the trade name 'Red Diamond.'