I did a tremendous amount of research before custom designing our 16-pin needle cartridges which are made out of stainless steel and titanium. I decided on 16 as it is less painful than 12 needles—the fewer needles, the deeper, they penetrate. 16 needles go to the proper depth for use on the face and elsewhere. Unlike other micropens that sell generic tips purchased in bulk, the AcuLift Micropen cartridges are custom-made for AcuLift. See photo above.