One issue with this design is that with the bubble at the very top it is extremely difficult to see that bubble without breaking cheekweld (unless you're a hammerhead shark), it also means your scope must be mounted perfectly perpendicular to your rings/base and some shooters like to mount their scope based on their natural hold which will cant slightly. Also, if you're a shooter with presbyopia then anything on that first ring is a blurred mess and if you put it on the second ring furthest from your eye it will be behind the turret again making it difficult to use. Outside of those issues the design is cool, but I like what ERA-TAC has done with an option for a bubble off to the side of the ring, see image below
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