Ready-to-use ELISA kits are available for the detection of p16 INK4a, an alias of the protein, cyclin dependent kinase inhibitor 2A. The official gene symbol is CDKN2A. The kits can detect several species variants of the protein, including: human, mouse, and rat. The protein, with a mass of 16.5 kDa and length of 156 residues, is reported to be cytoplasmic and nuclear. It is a member of the CDKN2 cyclin-dependent kinase inhibitor family and may be known by other names, including: ARF, multiple tumor suppressor 1, cyclin-dependent kinase 4 inhibitor A, cell cycle negative regulator beta, alternative reading frame, and CDK4 inhibitor p16-INK4, and CMM2.