A jar and screw cap that actually thread together, sized to whatever you need to store. The threads are true helical geometry from the CAD kernel — the same trapezoid profile the classic community screw-cap generator uses, with a blunt crest that prints cleanly and engages smoothly. The jar's inner diameter and height set the storage space; the thread diameter sets the mouth (and the cap follows automatically). Coarser pitch — 2.5 to 4mm — prints better and opens faster than fine threads. Fit clearance defaults to 0.4mm, which suits a tuned printer; loosen to 0.6mm if your cap binds. Print tip: jar upright, cap open-side up, no supports. PETG threads wear noticeably better than PLA for daily-use lids.