This 3M fryer oil test strip kit is a great way to test the shortening breakdown in your fryer. Hold the test strip by longest white end, dip test strip into hot oil so all of the blue bands are submerged. Hold in oil for 1-2 seconds, remove strip from shortening, and wait 15 seconds. Hold strip to light, compare strip to evaluation guide and follow recommendations; then throw away used test strip. Each vial comes with 40 test strips. Please consult the Specification Sheet for additional details.