3" diameter 38mm Dual Deployment rocket.  This is a sport flyer to give me something to fly 38mm motors with.  The fins are 3/4" wide at the base, 1/4" wide at the tip.  There is a 1/2" wide slot from tip to BT in each fin to make it whistle.

Update:  It doesn't whistle so the name has been changed to Dog Whistle.  This is Dog Whistle DD because it is the dual deployment version.