51143 series 6.5mm terminal position assurance (TPA) retainers for use with 6.5mm wire to board crimp receptacle housings locking the terminals in place inside the connector.
Stock number 905-9903 is a 1 circuit TPA for use with the 51142 series 6.5mm wire to board crimp housings
Stock number 905-9907 is a 2 circuit TPA for use with the 51142 and 151049 series 6.5mm wire to board crimp housings
Stock number 905-9916 is a 3 circuit TPA for use with the 51142 series 6.5mm wire to board crimp housings