Check the listing for details. SportDOG Add A Dog Receiver Extra Collar SDR-AXF SD-425 -425X-825-825X-575E-575. Condition: Used. Listed at 59.72 USD. SportDog Replacement / Add-A-Dog Collar SDT54-16292 removed from new SD-575 system with copy of retail store receipt for proof of purchase and warranty purposes ! Please Note: Includes only the used in perfect working condition receiver (as pictured) so you will need a compatible charger. Part Numbers: SDT54-16292, SDR-AF Compatible charger available link below :https://ebay.to/393287E The Collar Receiver for FieldTrainer 425X, SportHunter 825X and SportTrainer™ 575E/875E Remote Trainers. Add another dog to your current SportDOG Brand® electronic training collar system or replace a Collar Receiver with the SDR-AFX Add-A-Dog Receiver Collar. SYSTEM COMPATIBILITYFieldTrainer® 425X (SD-425X), 425XS (SD-425XS), 425 (SD-425), 425S (SD-425S)SportHunter® 825X (SD-825X), 1225X (SD-1225X), 1825 (SD-1825X), 825 (SD-825), 1225 (SD-1225), 1825 (SD-1825)SportTrainer® 575 (SD-575E), 875 (SD-875E), 1275 (SD-1275E)WetlandHunter® 425X (SD-425XCAMO), 1825 (SD-1825XCAMO), 425 (SD-425CAMO), 1825 (SD-1825CAMO)ProHunter® 2525 (SD-2525)HoundHunter® 3225 (SD-3225)UplandHunter® 1875 (SD-1875)