Horrible tolerances - Meprolight MEPRO FUBS - Self-Illuminated Folding Back-Up Rifle Sights

Wanted to like them, I support Israel every chance I get. However, these sights suck. The crossing piece intended to fit down within the groove of a Picatinny rail space is too fat, and the side-to-side clamping dimension is too narrow. This is the worst design, machining and molding error. If the side-to-side clamping tolerance were slightly generous, you could always make it right by continuing to tighten the crossing Allen bolt until snug. Even worse, in this (retarded) design, the top portion of the 'C' clamp shape actually begins on the mono piece which is the sight itself as opposed to the 'C' attached to the Allen nut being drawn closer during tightening. Maddeningly, this main piece is not wide enough to sit down flat on the Picatinny rail, even before you capture the Allen bolt into the 'C' clamp/nut and begin to draw the two together. Perhaps Israeli picatinny rails are more narrow (side-to-side) than American Mil-Spec, and have bigger spaces between adjacent Picatinny bars. It's also second rate to have 'illuminated' sights where the rear aperture has no illumination, it's the front sight post only. Also, neither front nor rear is spring loaded to pop up, you manually fold them upright. Very regrettable purchase.