ISO-QF (KF) Weld Ring Flange

Weld ring flanges were created to offer a thin profile while still offering a weld preparation groove. This groove makes the flange self-aligning, offers greater weld joint strength, and provides aesthetic coverage of the weld joint and heat discoloration that can appear after welding.



  • High Vacuum Rated to 1×10-8 Torr
  • Bakeable to 200°C
  • Compatible with all ISO standard vacuum flanges and fittings
  • Quick sealing and disassembly



  • Standard:
    • 304 Stainless Steel
    • 316 Stainless Steel


Product Notes

  • Internal Weld
  • Self-aligning
  • Designed to fit standard inch tubing O.D.’s
  • Thinner design than standard socket weld flanges­

*Dimensions are in inches unless otherwise specified

Part IDReference NumberA B C Bore Size 3D CADDrawingUnit PriceIn StockQty, Add To Cart
Part ID4000077Reference NumberQF16-075-RFA 0.76B 0.25C 0.17Bore Size 0.753D CADLoginDrawingLoginUnit Price$10.00714
Part ID4000078Reference NumberQF25-100-RFA 1.01B 0.25C 0.17Bore Size 13D CADLoginDrawingLoginUnit Price$10.00715
Part ID4000079Reference NumberQF40-150-RFA 1.51B 0.25C 0.17Bore Size 1.53D CADLoginDrawingLoginUnit Price$14.002873
Part ID4000080Reference NumberQF50-200-RFA 2.01B 0.25C 0.17Bore Size 23D CADLoginDrawingLoginUnit Price$21.001260