Manufactured in Switzerland, these oil level glasses and machine observation windows offer the maximum available clarity. Maximum visibility into the machine for many years, and observe flow rates, direction of flow or to check on the lubricant levels easily.

Oil level windows / sight glasses with a diameter up to 300 mm offer a large viewing area. Thanks to their ideal, simple design, they require no machine wall reinforcement and offer a simple one-step, self-locking fixation. With a temperature resistance of up to 130 °C and printing screen markings as per your requirement, The Swiss manufactured oil level windows provide a versatile, well tested and reliable system. 


  • One-step fixation
  • Self-locking
  • No thread required
  • No machine wall reinforcement needed
  • Absolutely oil tight
  • Up to 130° C (version M), up to 70° C (standard)
  • From diameter 22 to 300 mm
  • Pressure up to 0,6 bar, then guard ring
  • NBR (standard), VitonTM or silicon seals
  • With or without reflector
  • Oil level markings with screen printing

push fit oil glasses schematic

Oil windows push fit models

* standard = acrylic plastic, for temperatures up to 70 °C * * M = polycarbonate, for temperatures up to 130 °C * * reflector included up to size 38


 Oil Circulation Indicators with Thread: Model H

Model H Polymer indicator blister

 oil circulation indicator model H



  • With metric thread
  • Totally translucent polymer
  • Can be mounted vertically or horizontally
  • Complete with seal
  • Available in 3 materials:
  • Polyacryl - for up to 80 °C
  • Polyamide - for up to 100 °C
  • Polycarbonate - for up to 120 °C

Clear Observation Windows

clear observation window

Observation windows from size 75 mm upwards are frequently used as observation windows for checking of clutches, limit switches, etc.

Windows used in this way should be easily adjustable and replaceable, to facilitate the adjustment of the particular components. With this in mind, TEPRO observation windows are provided with an external grip/handle, by which they can be removed without difficulty and subsequently returned dust-proof, to their previous position.

clear observation window models


  • With built-in grip
  • One-step fixation
  • Self-locking
  • No thread required
  • No machine wall reinforcement needed
  • Up to 130° C (Version M), up to 70° C (Standard)
  • From diameter 75 to 300 mm
  • Pressure up to 0,6 bar
  • NBR (standard), VitonTM or silicon seals


Oil Level Glasses

brass oil level glass

The Oil Level Windows with Fixing Holes: Model TE in Brass is one of the many popular methods of quickly displaying lubricant levels.

TE window schematic

model te brass oil level indicator


  • Brass housing with two-part reflector
  • Can be tightened without draining oil
  • Supplied with a seal

Oil Level Windows: Model FE (Metal) 

Model FE oil level windowModel FE oil level window schematic

Models of FE oil level window



  • Frame lengths from 60 to 250 mm
  • Pressure resistance up to 10 bar/110 °C
  • Excellent clarity of display
  • Good petrol - gas/ diesel resistance
  • Durable, robust construction:
  • aluminium / natural glass
  • High-grade NBR gaskets

Oil Level Indicators: Model AS (Polymer)

AS Polymer oil level indicatorAS Polymer oil level indicator schematic

AS Polymer oil level indicator models


  • Fixation part of the screw is brass
  • Polymer level tube, can be rotated
  • Two-way venting
  • Oil level markings according to your Screen Print

Please contact Merlin Industrial with your application requirements for a speedy response.

Vat GB591551821 Company Number 02906480 – 1994
Dun and Bradstreet, Number (581590544)
NATO Code Number (NCAGE KD520)
EORI Number GB591551821000


Merlin Industrial Products @ 2024 Errors and Omissions Excepted


Call 01752 690622 / 0800 0418 650 (UK)