Standard Loc-Line type links are a pain to print because tiny variations in the printing process can affect the gripping friction dramatically. These links feature an adjustable clamping screw (4-40 x 1/2"L) that lets you adjust them from free-spinning to locked tight. They aren't designed fluids (like the original Loc-Line), but they are great for flexible mounts, 3rd hand jigs, and creature tentacles! (I hope I'll see a bunch of remixes/add-ons.)I print these with 0.2mm layers, 3 perimeters, and 20% infill. Make sure to de-burr the edge of the socket before assembling. The clamping screw is a 4-40 x 1/2" long. No need to tap the screw holes - the screw will form its own thread in the plastic as you screw it in. Make sure the screw is loose before snapping the links together or pulling them apart. In the base piece, the thru-holes are sized for #6 screws. The holes in the blockhead piece are also for 6-32 screws. You shouldn't have to tap these holes either, but if you are going to be repeatedly mounting and unmounting things to them, pre-tapping them will make life easier.