SnapIt! Wheelchair Adjustable Drink Holder 3/4" to 1-3/16" (19mm to 30mm) Four position adjustable drink holder for walkers, wheelchairs, scooters, etc. Holds a wide variety of drink containers from large 3 5/8" diameter bottles down to small water bottles. Includes SnapIt! System MultiMount Bracket with hardware for mounting to a wide range of inch and metric tubing sizes from 3/4" to 1 3/16" (19mm to 30mm). Snap in clip on SnapIt! System MultiMount Bracket is designed to fail in the event of accidental contact with a hard surface in order to protect the drink holder from damage. Technical Specifications SnapIt! Tubing Diameter Size Chart Fractions Decimals Metric Flat Length 3/4" .75" 19mm 2.356" 7/8" .875" 22mm 2.75" 1" 1" 25mm 3.142" 1-1/8" 1.125" 29mm 3.53" 1-3/16" 1.1875" 30mm 3.73" 1-1/4" 1.25" 32mm 3.927" Step 1) Find a piece of paper measuring at least 4" x 1" Step 2) Now wrap the piece of paper around the section of tubing you would like to mount your SnapIt! cup holder. Step 3) While the paper is wrapped around the tube, mark the end of the piece of paper with a pencil. This will measure the entire circumference of the tube. Step 4) Now measure from the end of the paper to the mark with a ruler. Step 5) Look at the table above. Find the "Flat Lenght" and it's correlating "Diameter in Fractions", "Diameter in Decimals" and "Diameter in Metric" Now you will have the diameter of the tube!