This thing replaces the clip that keeps a folded umbrella stroller folded. Ours was lost in luggage land.The STL is for 10-11mm diameter frame rods, which seems pretty standard for North American umbrella strollers. Both sides snap tightly onto the rods, but I added a channel for a zip tie to prevent history repeating itself.I banged it out in Sketchup, complete with manifold/watertightness errors; the STL is fixed in Netfabb Basic.Print it! It worked for me after only the most cursory calibration of the axes.One ring has a channel for a small zip tie: snap it onto a rod (e.g. the "back" rod) and optionally secure it with said small zip tie. The other ring has a bump: this side snaps on and off a nearby rod (e.g. the "seat" rod).