Open co-founder Gerard Vroomen has no problem one-finger lifting a bike he claims is the lightest 29er hardtail in the world.

There is no UCI minimum when it comes to mountain bikes, but if there was it’s safe to say two new concept bikes from Open would be flagged illegal. As it is the pair of hardtail 29ers on display at Eurobike (one fully rigid, one with a 60mm leaf spring fork) are both under the UCI’s 6.8kg minimum for road bikes.

This fully rigid steed weighs just 14.1 pounds.

The fully rigid Open weighs in at 6.4kg (14.1 pounds), while the suspended version tips the scale at 6.7kg (14.8 pounds). Both bikes are spec’d with a litany of lightweight parts and wheels from German-weight-weenie parts maker AX Lightness, plus SRAM XX1 drivetrains. The suspension fork is the yet-to-be-released 990-gram Lauf TR29, which uses glass fiber leaf springs instead of more traditional suspension mechanisms. Tires are Schwalbe Furious Fred. The cranks are THM Clavicula.

“We did it because we could,” explained Open co-founder (and former Cervélo) boss Gerard Vroomen. “They are exceptionally lightweight but they are still bikes that are fully functional and can be raced. These are not spec’d with crazy drilled out stuff that breaks when you look at it.”

Frame weight of the O-1.0 is under 900 grams for a size large, added Vroomen, who figures these are the “lightest 29er hardtails in the world.”

Vroomen also gave a thumbs up to the yet unproven Lauf fork. “I think one really big advantage is that it solves the problem of stiction,” he said. “Normally there’s a slight delay in the initial action of a fork, but not here. So over small bumps this fork reacts much quicker. But we still need to do some fatigue testing before we commit to spec’ing it on our bikes.”

However, Vroomen said that sort of testing has already been done with these two super light bikes. “We brought them to the testing agency here in Germany,” he explained. “And they said there were the lightest mountain bikes that have ever passed even though when we first brought them in they were sure that they wouldn’t pass.”

This proof-of-concept steed weighs less than the UCI minimum for road bikes.

The rigid Open is available as a fuselage only, meaning drivetrain and wheels are not included, and retails for $6,700. The suspended bike is simply a proof of concept and is not yet available for sale.