I'm not sure, if you take your bike to your LBS they will probably test if it will fit or not, my LBS have all the lights out on display but if they do fit you will be very impressed
Well, it was worth joining the forum for this thread alone

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For anyone else who was wondering the rear Moon Shield does fit the Giant Aero Vector Seatpost

I can place it right at the top of the seat post under the saddle and it is aesthetically quite unobtrusive and I reckon it may be visible from the moon.
My first Moon Mask got lost in the post and I had to wait 2wks before they sent me another but it was well worth the wait.
I can't believe how small it actually is. I thought it was a joke at first and my heart sank. But as soon as I switched it on I knew it was perfect for my needs. It is very in keeping with my very light bike. I'm going to keep it black though.
This will give you an idea of the size against an iphone 4
Unbelievable!