Screws onto the back of E Mount lenses, (the side facing the camera)2 Refined designs included (heavy duty / normal)Improvements: 'Graduated Sloped Latches / ledges' means Smooth and secure tightening even on low end low resolution printers. it will work just fine on 0.25mm layer height even on cheap 3D printers.Mesh has been checked and cleared of all errors.Slices without issues. Locks and tightens smoothly and nicely on lensesThe "E MOUNT" Text Indentation stamp is there to collect sand and dirt that would otherwise scratch lens when you turn / twist it. So any dirt goes there rather than rub against your lens.Comes in 2 designs:1)High impact double layer and thick wall for expensive lenses and 2)more economical single wall normal version.TIP: Don't Print in black, Only silly manufacturers do that.Print in White / bright colours so you can see it clearly and don't lose it in your bag or at night. Seriously, what were manufacturers thinking printing lens caps in black.