Apple USB Mass Storage Support for Mac

From Apple:

USB Mass Storage Support 1.3.5 is a set of USB Mass Storage Class drivers written by Apple Computer to support USB Mass Storage Class devices. USB includes the notion of Class drivers, a set of software components generally delivered by Operating System vendors that are able to communicate with not just one, but many different USB devices of a particular kind. This enables any number of compliant devices to be plugged in and start working immediately without the need to install additional software. Several Class Drivers are already included in Mac OS for its computers with USB, including a hub class driver and a composite class driver. Over time, Apple expects to offer new and updated Class drivers for USB. The Mass Storage Support software represents one of these class drivers and is intended to support devices that meet the USB Mass Storage Class specification. Version 1.3.5 addresses potential conflicts with multiple drivers attempting to control a single device.