I am relatively new to this but I was hoping somebody could offer up a good critique of this XML structure I put together. I am not looking for anything in depth but rather if somebody notices anything inherently wrong with the structure (or any tips to make it better) I'd greatly appreciate it.

We have a large amount of products that we wholesale out and our customers were looking for a data feed to incorporate our products into their websites.

<product modified="">
    <id></id>
    <title></title>
    <description></description>
    <upc></upc>
    <quantity></quantity>
    <images>
        <image width="" height=""></image>
        <image width="" height=""></image>
        <image width="" height=""></image>
    </images>
    <category>
        <name></name>
        <subcategory></subcategory>
    </category>     
    <sale expiration="">yes</sale>
    <msrp></msrp>               
    <cube></cube>
    <weight></weight>
    <pricing>
        <tier>
            <pack><pack>
            <price></price>
        </tier>
        <tier>
            <pack><pack>
            <price></price>
        </tier>         
        <tier>
            <pack><pack>
            <price></price>
        </tier>
    </pricing>
</product>

We sell in 3 different pack sizes hence the pricing node.