{
 "version": "2026-10-20",
 "license": "Dimension sheets: CC BY 4.0. Standard and published-size files: CC BY 4.0. Xem Studio's own designs (files_license = Xem Studio Design License): free to use and sell things from, not to redistribute as files — https://xemstudio.com/license/. Other publishers' files: their own license, linked beside them.",
 "slug": "l-mount",
 "name": "L-Mount: 20 mm flange focal distance, 51.6 mm diameter",
 "kind": "standard",
 "category": "Cameras & lenses",
 "group": "Lens mounts & filter threads",
 "year": null,
 "question": "What is the L-Mount flange focal distance and throat diameter?",
 "tags": [
  "lens mount",
  "camera",
  "lens",
  "mount",
  "adapter",
  "flange distance",
  "standard"
 ],
 "aliases": [
  "l mount flange distance",
  "l-mount diameter",
  "leica l mount dimensions",
  "l mount 51.6mm",
  "sigma l mount"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "not-scanned",
 "les": false,
 "free_files": 0,
 "url": "https://xemstudio.com/objects/l-mount/",
 "sheet_txt": "https://xemstudio.com/objects/l-mount/sheet.txt",
 "sheet": {
  "basis": "Published numbers only (sources per row); no bayonet geometry is published, so no file",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "Flange focal distance is the distance from the mount's reference face to the image plane; adapters and extension tubes must add exactly the difference between two mounts' flange distances to keep infinity focus.",
   "Shared by the L-Mount Alliance makers; full-frame and APS-C lenses use the same mount.",
   "No file: the bayonet's lug widths, angles, depths and locking geometry are not published by the maker, so nothing is drawn. Only the published numbers are given."
  ],
  "table": {
   "columns": [
    "parameter",
    "value",
    "from"
   ],
   "rows": [
    [
     "flange focal distance",
     "20 mm",
     "L-Mount Alliance"
    ],
    [
     "throat / inner diameter",
     "51.6 mm (diameter)",
     "L-Mount Alliance"
    ],
    [
     "coupling",
     "bayonet",
     "—"
    ]
   ]
  }
 },
 "sheet_text": "L-Mount: 20 mm flange focal distance, 51.6 mm diameter — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/l-mount/  (sheet CC BY 4.0)\nBasis: Published numbers only (sources per row); no bayonet geometry is published, so no file\nCatalog version: 2026-10-20\n\nSizes: see table below\n- Flange focal distance is the distance from the mount's reference face to the image plane; adapters and extension tubes must add exactly the difference between two mounts' flange distances to keep infinity focus.\n- Shared by the L-Mount Alliance makers; full-frame and APS-C lenses use the same mount.\n- No file: the bayonet's lug widths, angles, depths and locking geometry are not published by the maker, so nothing is drawn. Only the published numbers are given.\n\nparameter  value  from\nflange focal distance  20 mm  L-Mount Alliance\nthroat / inner diameter  51.6 mm (diameter)  L-Mount Alliance\ncoupling  bayonet  —\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- L-Mount Alliance: L-Mount overview (51.6 mm diameter, 20 mm flange distance) — web — Publisher's page; dimensions are facts — https://l-mount.com/en/Overview\n- Wikipedia: Flange focal distance (table of mounts) — web — CC BY-SA 4.0 (text); dimensions are facts — https://en.wikipedia.org/wiki/Flange_focal_distance\n\nNo true-size file yet: the published figures do not fix the whole shape; a measured scan is planned.\nAPI: https://xemstudio.com/api/geometry?object=l-mount\n",
 "sources": [
  {
   "publisher": "L-Mount Alliance",
   "title": "L-Mount overview (51.6 mm diameter, 20 mm flange distance)",
   "url": "https://l-mount.com/en/Overview",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Wikipedia",
   "title": "Flange focal distance (table of mounts)",
   "url": "https://en.wikipedia.org/wiki/Flange_focal_distance",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text); dimensions are facts",
   "license_verified": true,
   "hosted": false
  }
 ],
 "xem": {
  "status": "not-scanned",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "sony-e-mount",
  "canon-rf-mount",
  "micro-four-thirds-mount"
 ],
 "fits": [],
 "dimensions": "exact (nominal, no printing tolerance)",
 "dimension_rule": "All geometry on Xem Studio is exact (nominal, true size) with no printing tolerance. Where a part meets another part, the object lists its mating features (feature, exact size, what it mates with, fit class: press, slide, run, socket, clamp or designed). Apply your process's allowance to those features only; 'designed' gaps are part of the design and stay as drawn.",
 "mating": [],
 "faq": [
  {
   "q": "What is the L-Mount flange distance?",
   "a": "20 mm, with a 51.6 mm diameter (L-Mount Alliance)."
  }
 ],
 "files_license": null,
 "offers": [],
 "markdown": "https://xemstudio.com/objects/l-mount/index.md"
}