These bulk pack acrylic sight glass tubes are intended for use as a vacuum trailer, Vacuum Truck and frac tank sight glass. It's most popular use is as a visual fluid level gauge. The sight glass is a round, clear, acrylic extruded tube. It is durable, scratch-resistant and slightly flexible.The tube has an outer diameter of 2-3/8" and an inner diameter of 1-7/8" with a 1/4" thick wall. This item is priced and sold as a case of four (4) sight glass tubes. Each tube is 72" long (6 ft). If you need a shorter length, we can cut this item down to meet your requirement. Please contact custom service for more details on custom lengths.