It’s made from Borosilicate, it is used in lever gauge in boiler for water position.
It is also named:  Reflex Gauge Glass, Sight glass, Reflex Glasses
Reflex sight glass, Spares For level Gauge
The category is as follows:
1) Three tendons (four grooves)
2) Two tendons (three grooves)
3) Plan transparent

Three tendons (four grooves)
Size:
340 x 34(30) x 17mm 320 x 34(30) x 17mm,
280 x 34(30) x 17mm
250 x 34(30) x 17mm, 218 x 34(30) x 17mm,
190 x 34(30) x 17mm
165 x 34(30) x 17mm, 140 x 34(30) x 17mm,
115 x 34(30) x 17mm
The other size is optional or according to the requirements of customers.
Working temperature: 260 ℃, Working pressure: 4.0MPa

Two tendons (three grooves)
Size:
340 x 34 x 17mm 320 x 34 x 17mm, 280 x 34 x 17mm
250 x 34 x 17mm, 218 x 34 x 17mm, 190 x 34 x 17mm
165 x 34 x 17mm, 140 x 34x 17mm, 115 x 34 x 17mm
The other size is optional or according to the requirements of customers.
Working temperature: 260 ℃, Working pressure: 4.4MPa

Transparent plane
Size:
340 x 34 x 17mm, 320 x 34 x 17mm, 280 x 34 x 17mm
250 x 34 x 17mm, 218 x 34 x 17mm, 216 x 34 x 17mm
190 x 34 x 17mm, 165 x 34 x 17mm, 215 x 34 x 22mm
218 x 38 x 23mm, 190 x 38 x 23mm, 165 x 38 x 23mm
The other size is optional or according to the requirements of customers.

Working temperature: 260 ℃, Working pressure: 8.0 MPa

Level Gauge Glass Physical Property

1. Appearance

1) Air bubble:
Diameter≤0.5mm,in the 10mm x 10mm area the quantity must be ≤3.
Diameter from 0.5mm to 1.5mm dispersive air bubble,there is less 2 on the sight plane and less 5 on the No-sight plane. Their distance must be ＞40mm.
The air bubble of Diameter from 1.5mm to 2mm ≤3  on the No-sight plane. Their distance must ＞40mm.
On the sight plane, The distance to the side in 7.5mm,the air bubble of the  diameter＜1mm mustn’t be more 2.
2) The glass don’t allow slag and scrap iron,etc. impurity.
3) Stripe : don’t allow have palpable filaceous and pectinate stripe on the sight plane.
4) Cockle: In the side face,don’t allow have the cockle of depth ＞1mm.
5) Crack: don’t allow have crack.
6) Scrape: On the sight plane and in the 7.5mm to edge,the scrape of less than 10mm don’t allow more 2 strips.
7) The sight plane must be polishing,and sealing side must be rubbing and polishing.

2. Colour and Lustre

It should be no color and transparent，and with its self tine green is allowed.

3. Water-resistance

Cooked in the water for 5 hours，then weigh up ，then titration with 25ml    0~31    ug/g

4. Alkali-resistance

Cooked in the 0.5N NaoH for 3 hours，then Weigh up，weightlessness should be ≤75  mg/dm2

5. Temperature-resistance impacts capability

Put it into electric cooker，keep for 7min under the temperature of 260℃±1℃，then，put into the water of 20±1℃，it should not crack

6. Bend-resistance

≥80 MPa