Frog eye sight glass NPT thread high temperature resistant screw oil sight glass

Frog Eye Sight Glass — NPT Thread Screw-In Oil Sight Glass

The frog eye sight glass (also known as a bull's eye sight glass) is a compact, screw-in oil level indicator designed for direct installation into gearbox housings, compressor bodies, pump casings, and other industrial machinery. Its distinctive circular borosilicate glass window provides a clear, wide-angle view of oil levels and condition without requiring any additional fittings.

Key Features

• Borosilicate glass window — high thermal shock resistance, rated for high-temperature service
• NPT threaded body for direct screw-in installation — no additional fittings required
• Compact, low-profile design — minimal installation space required
• Corrosion-resistant aluminium alloy or stainless steel body
• Oil-resistant sealing gasket included
• Available in multiple thread sizes: 1/4", 3/8", 1/2", 3/4", 1" NPT

Specifications

• Glass material: Borosilicate (high-temp resistant)
• Body material: Aluminium alloy / Stainless steel 304
• Thread standard: NPT (BSP available on request)
• Max working temperature: 120°C (standard) / 180°C (high-temp version)
• Max working pressure: 0.3 MPa
• Suitable fluids: Mineral oil, synthetic lubricants, hydraulic fluid

Typical Applications

• Industrial gearboxes and speed reducers
• Screw and reciprocating air compressors
• Hydraulic power units
• Pumps and electric motor bearing housings
• Machine tool lubrication reservoirs

Available in standard NPT sizes. BSP thread and stainless steel body options available on request. Contact us with your thread size and operating conditions.