i'm pretty sure the standard is in ounces, making it:
5.29 oz.
i also would like to know how much a DS game weighs. i'm shipping some games out as well this week.
free bump!
First class mailing in a bubble mailer usually runs me about 2.75 (with delivery confirmation) for most current gen games (obviously a little weight difference depending on how big the instructions are) and ds games maybe $.50 less if even that much difference.