Criticare SpO2 finger sensor is a dirct connect to the monitor with a 10 foot cable. It can also be used with an extension cable and is compatible for the following SpO2 monitors: Alaris (IVAC): VitalCheck 4400 511SD; Criticare: 503DX-W, 503S, 503DX, 503 Spot, Mini Spot, 504DX/P, 504DX, 506 series (except 506LN3), 507ELC2, 507EL, 8100 series, Poet Plus, Poet (602-3A), Scholar, Scholar III