Truelok® offers a wide range of face seal fittings, mini weld & micro weld fittings and VCR* style fittings with surface finish down to 5 Ra, with or without electropolish. These fittings deliver outstanding performance in gas delivery systems and in the instruments to certify the purity of gases and the integrity of gas delivery system in the semiconductor industry. Truelok® fittings are interchangeable and intermixable with the fittings offered by other manufacturers. Truelok® specializes in producing high quality internal finish with Ra values less than 5. Our standard finish is 10 Ra. Several proprietary techniques have been developed for producing surface finish with low Ra values, proper surface chemistry, and high purity contamination-free components. A component’s surface finish is verified using profilometer and high-resolution microscopes are used to ensure a high luster finish.

Face Seal Fittings - Technical Information

Material Specification:

Weld Fittings
Micro Weld / Forged Weld Fittings
MaterialConforming Specifications
316L Stainless SteelASTM
A182 A262A269A276
EN 1024 Type 3.1
316L Stainless Steel VAR JIS
Metal Face Seal Fittings
Glands, BodiesGaskets
Material Conforming SpecificationsMaterialConforming Specifications
Stainless Steel
A182 A262A269A276
EN 1024 Type 3.1
316L Stainless Steel VAR JIS316L Stainless Steel VAR ASTM B167

Material Composition:

Chemistry of a few basic elements for comparison (Avg. Wt. %)

Pressure Rating (SS 316L):

Working pressures are rated at ambient temperature and are based on a 4 to 1 design factor. To determine pressure ratings in accordance with ANSI B31.1 multiply pressure rating by 0.94.
SizeWall Thickness Pressure Rating

Temperature Rating:

Face Seal & Mini Weld FittingsSS316L1000538
SS316L VAR or VIM/VAR 1000538
Face Seal GasketsSS316L1000538

Surface Finish:

Truelok® Face Seal & Mini Weld Fittings are offered in the following surface finishes:
FinishElectropolishedRa Value (Max)Ra Value (Avg)

Electropolished Face Seal and Mini Weld Fittings:

Components are electropolished to provide oxide layer on the metal surfaces. This process prevents adsorption of gases and moisture on the surface to a greater degree and removes any contaminants adhered to the internal surface of the fittings. It also helps reduce friction and wear of the component. Moreover, due to enhanced smoothness of the electropolished wetted surface, build-up of products on the surface and any bacterial growth is reduced and provides with improved reflectivity of the finished surface. Following is the surface analysis report of a typical Truelok® Electropolished face seal component:
Cr/FeCrOX/FeOXTest Method
3.25.2XPS Sematech Standard 90120403B

Silver Plated Nuts and Gaskets:

Threads of Female Nuts are silver plated to reduce the risk of galling and to improve re-make ability of the fitting. It also improves torque for the fitting assembly. Silver plated gaskets also reduce friction during assembly of fittings.

Cleaning and Packaging:

Ultra-High Purity cleaning and packaging in a Class 10 Clean Room environment validated per Federal Standard 209E, is standard for all electropolished components.


Truelok® face seal – VCR* style glands provide high integrity metal to metal seal, giving leak-tight service from vacuum to positive pressures (see pressure ratings). Such assemblies easily pass leak tests down to 1 x 10-9 std cm3/s.
The seal between two face seal glands is made when a gasket is placed between and compressed by the beads of the two glands during the engagement of a male nut or body hex and a female nut (see detailed instruction below).
Visual test and leak test are performed through two test ports in opposite locations from the female nut.

Face Seal Glands - VCR* Style Glands - Make-up Instructions:

  • Align the two sealing surfaces ensuring the toroid beads of the two glands squarely face each other.
  • Insert a VCR* Style metal gasket between the two toroids; if possible, use gasket with a retainer ring.
  • Tighten the female nut to the male nut/body finger tight.
  • Use two wrenches. Hold the male nut stationary with one wrench and tighten the female nut with the second wrench by 1/8 turn past finger tight.
  • Caution: Always torque the female nut while keeping male nut/body stationary.
  • Face Seal Connections are re-makable. However, use of a new gasket for each re-make is highly recommended. Face Seal Fittings need to be handled with great care until assembly and make-up. Sealing toroid of the glands are protected with caps, do not remove the caps until ready to make a seal. The sealing surfaces should never be scratched, damaged, or contaminated in any way during handling and assembly.
  • Always employ proper cleanroom protocol for make-up and assembly of high-purity fittings and applications.

*VCR is a registered trademark of Swagelok company, Truelok® is not affiliated with Swagelok company.