Duragrouch

It works, reduces hinge flex and wear. There's nothing else they could have done that improved frame bending strength so much, was so light, was so cheap, and didn't impede folding. "Lighter than air, stronger than steel, cheaper than dirt." I was gonna make my own from sailboat stainless steel standing rigging, but just rigged a double line of kevlar looped around the head tube and bottom bracket shell, worked great, been on almost a year and still tight, no stretch. Dahon is supposed to offer a retrofittable version this year, secured to same places as mine, I'll believe it when I see it available here, and at good price.