McMaster Carr Steel Knurled Head Thumb Screw

Manufactured by McMaster-Carr
SKU: 92581A320
Manufactured by McMaster-Carr
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NOTE: Limit 5 per household. Quantities exceeding 5 will not allow checkout.

We are fully staffed and processing orders. Standard orders are shipping in approximately 7 business days. FFL orders take approximately 20 business days or less if you can provide us an actively receiving FFL location.



AR15 carry handle sights are durable, practical, and versatile, but leave much to be desired in the optics mounting category. With this McMaster black oxide steel thumb screw, you can easily attach our Primary Arms Prism Scopes to the carry handle to increase your medium range capabilities. The head of the thumb screw is knurled to make tightening it down with your fingers easy and will make sure your optic is rock solid to retain zero. This screw only works with Primary Arms 2.5X, 3X, and 5X prism scopes.

  • Only fits Gen 1 Primary Arms 2.5X, 3X, and 5X prism scopes (not newer models)
  • Black oxide steel screw
  • Knurled head for increased grip
  • M5 threads
  • 8mm long
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TypeKnurled Thumb Screw

WARNING: This Product can expose you to chemicals which is known to state of California to cause Cancer and Reproductive Harm. For more information, see

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