uxcell Oil Liquid Level Gauge Sight Glass G3/4 Male Threaded Brass Air Compressor Fittings with O-Ring, Yellow - - Amazon.com
Amazon.com: Beduan in-Line Sight Glass with Tri Clamp End, Sanitary Flow Sight Glass Stainless Steel 2 Inch Tri Clamp Type (Flow Pipe OD 51mm) : Industrial & Scientific