Inline double window flow sights can be used to determine flow, clarity of fluid and impurities in either horizontal or vertical pipe runs. Nylon ball flow indicator gives positive flow indication with dark or opaque fluids. Standard Features: 1/2, 3/4, 1 or 1 1/2 inch PTF female connection Temperature Rating: Maximum working temperature up to 180°F (82°C) For applications requiring maximum working temperature over 180°F (82°C), please consult factory Caution: Scratched glass significantly reduces pressure rating.