A grommet turns a raw drilled hole into a finished pass-through: two halves press together from opposite sides of the panel, hiding the cut edge behind a flange on each face. Measure two things — the hole diameter and the panel thickness — and the press fit is computed for you. The cable hole is the opening left through the middle; the flared mouth option rounds its edges so insulation never chafes. Total thickness sets how proud the flanges sit (a few mm beyond the panel reads as intentional trim). The blanking version omits the hole entirely — the clean way to retire an old cable hole. Print tip: both halves print flange-down with no supports. The default 0.05mm interference gives a firm tap-together fit; if your printer runs tight, raise tolerance to 0.1.