A retainer for use with a fastener cartridge that is locked to the fastener cartridge until the fastener cartridge is inserted into a fastener cartridge channel of a surgical fastener. The retainer can include one or more deflectable tabs that engage the fastener cartridge. The one or more tabs can be displaced when the fastener cartridge is fully installed in the fastener cartridge channel such that the tabs disengage from the fastener cartridge, enabling a user to remove the retainer. In certain embodiments, tabs can extend from a body of the retainer and can engage exterior portions of a fastener cartridge. The tabs can be displaced outwardly by the fastener cartridge channel. In certain embodiments, tabs can extend from one or more movable portions that engage a slot in the fastener cartridge. The tabs can be displaced inwardly when the movable portions are deflected by the fastener cartridge channel.