The weight is either 30 or 35 lbs. for both, I can't remember which: One of the guys from Truax would know for sure. I haven't noticed any difference in acceleration due to the added weight.
Shipping was included in the $300 I paid, but the TMS website now says $325.
Thanks for linking the pictures, Kramer.
There are some more pics of these on the Maxima.org thread that Dan Truax links to in post #53 of "Chassis bracing, who is interested??":
6th Gen Maxima and Altima 02-06 Chassis brace group buy - Maxima Forums
