The Full Metal Bracket for Gazelle Kwikstep will only fit the third version of the Kwikstep as shown here on the photos (the one with 22" wheels) The diameter of the clamps is 34 mm at the front and 38 mm at the back side, which corresponds to the diameter of the Kwiksteps headtube with the half lug construction. I only made one of it and it's sold, but I can make a second one on request. Just send me an email.
Note the bike you have in mind should have a tall enough headtube for a Brompton luggage frame (or a bag with the frame in it). Most luggage frames are 30 cm tall excluding the handle. Also take into consideration that you need some 5 cm for putting the bag on the bracket and taking it off again. Cables (or lines) can be interfering with the bag, so you need to route them close to the headtube. Also consider the position on the headtube where you would want to install it. The lower the better, because it gives more room for the bag which sits mostly on top of the bracket, but the down tube (and the lug or welds/brazes) might interfere with the clamps. The spacing between both clamps is 47mm in case a lug or downtube connection should fit in between
Material: 5 mm stainless steel AISI 304 Stone tumbled RAW uncoated, Tig welded and silver (55%) brazed, final finish with Scotch Brite
Hardware: A2 quality stainless steel hardware for the latch hinge and clamp, stainless steel spring made in Sweden
Weight: 220 gram
Load capacity: more than you can handle, check the reel on my Instagram account where I (75kg+) stand on a 11kg vice which is hold by the FmB
Included is a leather lace and a tie wrap to install according to the last three photos of my P01 prototype Allsteelcarrierblock
Also included is the Full Metal Bracket - "Make bikes not war" card on 300 grams 100% recycled paper in a small size of 105x105mm. A bigger A5 size poster can be ordered as extra.
More photos in the dedicated Instagram my stories folder
The assembly instructions in the video below don't really apply, or only partly, to the clamp-on version. You don't have to take the clamp-on version apart prior to installing it. But it gives a good understanding of the product as it's quite similar.