Many Fluorescence Polarization (FP) reading instruments require the use of a reference standard for internal calibration of the reader. The FP One Step Reference Kit contains reagents to use as green or red FP references in a single tube or a microplate high throughput screening (HTS) instrument. The green reagents can be used for readings using the following filters: 488 nm ± 5 nm for excitation and 535 nm ± 5 nm for emission (or equivalent). The red reagents can be used for readings using the following filters: 525 nm ± 5 nm for excitation and 590 nm ± 5 nm for emission (or equivalent).