Whats the difference between Co-Witness (this model CM305) and the 1/3 Co-Witness (CM304)?

According to the manufacturer, the CM305 is an absolute cowitness mount- when mounted directly to a flattop AR receiver and standard height iron sights are attached as well, the optics' reticle (dot in this case) should align perfectly with the iron sights (at the top of the front sight post when everything is zeroed in). The CM305 is a lower 1/3 cowitness mount, meaning the iron sights will be visible through the optic in the "lower one third" of the sight picture. With all this said, at the end of the day the CM304 is a slightly taller mount than the CM305. Two different ranges can be zeroed when using the CM304 (one range with iron sights, a different distance with the red dot). Something else to consider is if your optic has a BDC reticle, the longer ranges of the reticle may not be usable, as your front sight post will be between the reticle and your target with the CM305 unless your iron sights can be flipped down out of the way... Good luck.

Brand	Vortex
Color	Black
Style	Absolute Co-Witness
Sport	Hunting
Item Weight	68 Grams
Material	Aluminum
Magnification Maximum	1
Objective Lens Diameter	30 Millimeters
Magnification Minimum	1 x
Compatible Devices	Cross Bow
Mounting Type	Cantilever Mount
Night vision	No
Model Name	Sport Cantilever 30mm Ring - Absolute Co-Witness \| 1-inch Offset
Manufacturer	Vortex Optics
UPC	875874005228
Global Trade Identification Number	00875874005228
Item Package Dimensions L x W x H	7.87 x 4.65 x 3.07 inches
Package Weight	0.17 Kilograms
Item Dimensions LxWxH	7 x 1 x 9 inches
Brand Name	Vortex
Warranty Description	Unlimited, unconditional, lifetime warranty.
Suggested Users	unisex-adult
Number of Items	1
Part Number	CM-305
Model Year	2016
Included Components	cantilever ring mount
Size	30MM

Vortex Optics Sport Cantilever 30mm Rings

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