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T-SM4RR - SM4 Retaining Ring for Ø4" Mounts

Fosco Connect Part No.: T-SM4RR

  • $ 32.00 or

T-SM4RR - SM4 Retaining Ring for Ø4" Mounts

Product Drawing

  • Standard Retaining Rings for Optics Ranging from Ø75 mm to Ø4"
  • Thread SM4 (4.035"-40)
  • Thickness 0.13" (3.3 mm)
  • Clear Aperture Ø3.81" (Ø96.8 mm)

Our Standard Retaining Rings are manufactured from anodized aluminum and are offered in sizes to match our optic mounts and lens tubes, are designed to maximize the clear aperture while providing sufficient holding force. Securing an optic using a retaining ring is a stable method for holding the optic since the optic is retained along its entire edge instead of just at a few points. Each retaining ring is machined with two slots for compatibility with our selection of spanner wrenches.

T-SM4 (4.035"-40.0) Threading
Internal Thread, UNS-2B External Thread, UNS-2A
Min Major Diameter 4.0350" Max Major Diameter 4.0337"
Min Pitch Diameter 4.0188" Min Major Diameter 4.0286"
Max Pitch Diameter 4.0245" Max Pitch Diameter 4.0175"
Min Minor Diameter
(and 83.3% of Thread)
4.008" Min Pitch Diameter 4.0131"
Max Minor Diameter
(and 64.9% of Thread)
4.014" Max Minor Diameter 4.0066"


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