The Sight Glass

Detect Lubricant Problems Fast

Luneta's new Sight Glass has all the clarity and durability you need, with none of the leaks, cracks or squinting you may be used to with those old-style oil sight glasses. You'll never have to use fragile, dark, hard-to-read oil sight glasses again!



  • One-piece, high-impact Tritan™ construction
  • Outdoor Compatible: UV-resistant & withstands long-term sun exposure.
  • Resistant to chemical wear and buildup
  • Integrated threads mean no leaking


  • The Sight Glass extends from the machine, providing a clear view of oil
  • Molded-in hex nut means a quick, simple installation
  • Integrated eyelet for attaching lubricant ID tags or other pertinent information speeds up visual inspection and prevents confusion


  • Tritan™ construction means this oil sight glass is ultra-thin & super-clear with no distortion/discoloration
  • Etched, painted cross-hairs won't fade, rub off or distort the perceived oil level
  • Flat front surface allows for use of light or lasers to check for particulate – with no light deflection

Guaranteed Unbreakable

Thread Size NPT BSPP
1.0" Available Available
0.25" Available Available
0.375" Available Available
0.5" Available Available
0.75" Available Available
1.25" Planned N/A
1.5" Planned N/A
Thread Size Metric
M10x1.0 Available
M10x1.5 Available
M12x1.5 Available
M16x1.5 Available
M20x1.5 Available
M22x1.5 Available
Application Photos


Install in 5 easy steps

  • Apply thread sealer to the threads before installation.
  • Hand-thread the Luneta Sight Glass into the port.
  • Use a crescent wrench or 1-5/16" socket wrench to tighten until the hex nut contacts the port face (or if applicable, until the O-ring is compressed).
  • Check for leaks and apply more thread sealer if necessary.
  • Do not overtighten.
Sight Glass 1" 0.75" 0.5" 0.375" 0.25"
Wrench 1-5/16 1-1/8 7/8 3/4 5/8
Recommended Temp. Range -40°F to 200°F / -40°C to 93°C
Max. Operating Pressure 65 psi/4.48 bar
Comparison Luneta Sight Glass Acrylic Sight Glass
Impact Resistance (Joules) >40 8.9
Toughness or Durability (Notched Izod, 23-deg C, J/cm) 9.8 0.2
Wall Thickness (Thinner = Clearer) 0.19" 0.25"
Chemical Resistance Excellent Poor