MSS SP-43
Wrought and fabricated butt-welding fittings for low-pressure, corrosion-resistant service
Covers wrought and fabricated buttwelding fittings for low-pressure, corrosion-resistant service — typically thin-wall stainless fittings in schedules 5S and 10S, and stub ends for lap-joint flanges.
- Dimensional standards
Reviewed by the Kanak Steel & Engineering Co. technical team · Updated October 2026
What is MSS SP-43?
MSS SP-43 is the standard for wrought and fabricated buttwelding fittings for low-pressure, corrosion-resistant service — light-wall stainless fittings in Schedule 5S and 10S, plus short-pattern stub ends. Stainless fittings to SP-43 are ordered as ASTM A403 CR grades (e.g. CR316L, CR904L). For full pressure-piping fittings use ASME B16.9.
MSS SP-43 at a glance
| Walls | Schedule 5S and 10S (stub ends also in 40S short pattern) |
|---|---|
| Material | ASTM A403 CR grades for stainless |
| Typical use | Low-pressure water, chemical and process lines |
How to write MSS SP-43 on a purchase order
Name the product, size, material specification and grade, the dimensional standard and the certificate. An example line:
Illustrative only — sizes, tests, inspection level and any project values come from your purchase specification.
MSS SP-43 edition and verification status
Which edition we have confirmed, and what is still being checked before any numerical requirement is published here.
| Current edition | Not yet confirmed against the publisher listing |
|---|---|
| Full-text verification | In progress — numerical requirements are not published on this page |
| Edition on your order | The edition named in your purchase order or design code governs — confirm it with your enquiry |
What to know before ordering to MSS SP-43
The points that decide whether material to MSS SP-43 is accepted at inspection.
- SP-43 fittings are rated for lower pressure than B16.9 fittings.
- Fittings to SP-43 are marked Class CR under ASTM A403 or A815.
- Short-pattern (MSS) stub ends are defined here; long-pattern stub ends are in ASME B16.9.
Products made to MSS SP-43
How MSS SP-43 fits into an order
A purchase order line is only complete when it names the material standard, the dimensional standard and the inspection document. Miss one and the mill, the inspector and the buyer can each read the order differently.
Standards used with MSS SP-43
Same family
MSS SP-43 — questions buyers ask
What is MSS SP-43?
MSS SP-43 is the standard for wrought and fabricated buttwelding fittings for low-pressure, corrosion-resistant service — light-wall stainless fittings in Schedule 5S and 10S, plus short-pattern stub ends. Stainless fittings to SP-43 are ordered as ASTM A403 CR grades (e.g. CR316L, CR904L). For full pressure-piping fittings use ASME B16.9.
How are SP-43 stainless fittings designated?
With the ASTM A403 CR prefix — CR304L, CR316L, CR904L. CR grades have no construction class.
What is the difference between SP-43 and B16.9?
SP-43 is a light-wall, low-pressure standard; B16.9 covers all schedules for pressure piping.
Does MSS SP-43 specify the material?
No. MSS SP-43 sets dimensions; the material comes from a separate specification such as ASTM A182, A105 or B564 for flanges, or A403 and B366 for fittings. A complete order names both.
Sources: the ASTM / ASME specifications named on this page and producer datasheets · Last updated October 2026