Over the last couple years I’ve started using taller optic mounts even with fold down BUIS because they give me more FOV over a 12 o’clock mounted light and I can keep my head more upright.
I’m starting to realize however that what I thought was an industry standard for “absolute” co-witness and “lower 1/3” co-witness is really whatever each manufacturer feels like it should be. I ordered a Geissele RDS Mount and got the lower 1/3 version. It arrived and looked lower than I expect. I double checked part numbers and photos on their site. It is their “lower 1/3” and is taller than their absolute.
The thing is, it’s the same height as ADM’s “absolute” and the Aimpoint LRP with 39mm spacer (which is also listed as “absolute”). It’s a smidgen shorter than the DD mount with the “lower 1/3” spacer. Did everyone but me already know this? It wouldn’t be the first time I’m late to the party but damn what a disappointment.