GET to list all files for the specified product...

/api/v2/products/:sku/files
/api/v2/products/:sku/files.xml

Example result...

<?xml version="1.0" encoding="UTF-8"?>
<files type="array">
    <file>
        <id>123</id>
        <filename>Part1.zip</filename>
        <size_bytes type="integer">9774173559</size_bytes>
        <content_type>binary/octet-stream</content_type>
        <permalink href="http://demo.fetchapp.com/permalink/yuurud">/permalink/yuurud</permalink>
        <url nil="true"></url>
    </file>
    <file>
        <id>432</id>
        <filename>External File Name</filename>
        <size_bytes nil="true"></size_bytes>
        <content_type nil="true"></content_type>
        <permalink href="http://demo.fetchapp.com/permalink/werwa">/permalink/werwa</permalink>
        <url>http://your.cdn.com/link/to/file</url>
    </file>
</files>

For files stored in FetchApp, the url will be nil. For files stored externally the size_bytesand content_type will be nil since this information isn't available.