Similar item with a rounder shape by UK manufacturer, "Bendz".
They look like pretty decent LST aids. Probably good if you only have a few plants... I wouldn't want to buy hundreds of them to manage a larger crop.
Plant would look pretty gorgeous if you mainlined it and used these to make a supernaturally symetrical plant.
At home DIY version... hard plastic straws? Wide bottle caps? Using the corner of a clothes hanger as a splint? Eh. Too finicky.