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Strait-Flex® OS-400

DESIGNED for outside 90° corners where large voids and irregularities occur

Diamond-punched paper edging allows for easier feathering, faster drying, and the highest bonding strength.

Application(s): Drywall

OS-400 can also be used on double 5/8" drywall applications.  The diamond-punched paper edging allows for easier feathering, faster drying, and the highest bonding strength. Also guarantees an even lay-down of the paper, providing maximum adhesion with no rippling or blistering.  Apply with all-purpose joint-compound.

  • Double 5/8" drywall applications and outside 90° corners where there are large drywall irregularities
  • Clean installation
  • Composite backing provides a tough, durable corner with no rust
  • Nose resists dents and ensures perfect corners without paper fuzz-up during finishing and sanding


  • Measure wall height and subtract 1/2”. Measure and cut OS-400 using a scissors or utility knife.
  • With a 4” or 5” taping knife, apply a smooth, liberal coat of all-purpose compound to corner.
  • Press OS-400 into the wet compound. Adjust if necessary to create a straight line.
  • Wipe down tight with taping knife using a little additional pressure on the outer edges of OS-400. Immediately apply a light skim coat of compound over surface. Wipe down tight and smooth. Let dry completely over several hours or overnight.
  • With a 6” or 8” taping knife, apply your final coat of compound feathering the compound beyond previous coat. Let dry completely over several hours or overnight
  • Sand lightly with 120 grit sandpaper. OS-400 will not fuzz-up like paper or mesh tapes.

Code Approvals & Performance Standards


All stored materials shall be kept dry. Materials shall be stacked off the ground, supported on a level platform, and protected from weather and moisture.

Product Submittal Sheets

Click the below Product Code to view Submittal/Tech Datasheet.

Product Code Description
OS-400 Strait-Flex OS-400

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