Camerasize listed the a6600 to their site along with the E 16-55mm F2.8 G and E 70-350mm F4.5-6.3 G OSS. You can compare them here for yourself, here. I have been busy today, but I noticed there are some doctored comparisons out there that show the new sony glass as noticeably smaller than the competitors, which in my opinion is unnecessary.
Sony really knocked it out of the park and now Fujifilm has some serious APS-C competition, which is good for all of us. Also, the a6600 is very similar to the a6100 in size, but the grip is a little smaller.
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Sony a6600: B&H Photo / Amazon / Adorama
Sony a6100: B&H Photo / Amazon / Adorama
E 16-55mm F2.8 G: B&H Photo / Amazon / Adorama
E 70-350mm F4.5-6.3 G OSS: B&H Photo / Amazon / Adorama