O-Ring tools are components that help with the installation and proper function of an O-Ring. An O-Ring is a seal in the form of a ring with a circular cross section, typically made of rubber and sit within a groove or channel between two parts to create a tight, leak-free seal.O-Ring GaugesO-Ring gauges help to determine the right size of O-Ring to use. They have a series of silhouettes to the side of the gauge that identifies small section O-Ring sizes. Larger sizes are determined by placing the O-Ring around the two halves of the appropriate spindles at the top of the gauge. The slide is then extended and the size number is displayed in a window of the main body of the gauge.O-Ring TestersAn O-Ring tester is a compact tool that performs a non-destructive field test of an O-Ring by releasing a weight that falls to a set distance to indicate the material composition. O-Ring testers are typically made from durable stainless steel which allows them to be carried safely in tool boxes.