what's the term called

[fell]

When you have peep type sights and also something like a red dot sight, and set it up so
that when you are looking thru the peep sight, it's aligned with the red dot also?
It's on the tip of my tongue.....co- something, I think.
Someone help me with this term?

[Flash]

Co witness

[TheJediknight]

GOOD JOB

[deserttrans]

[Ballistic Therapy]

Co Operate ?

[freefly]

Co witness

Just to add / clarify:

If the optic's reticle/dot "lines up" with the irons, it's referred to as "absolute co-witness".
The benefit here is lower above-bore height, and no potential issues with cheek-weld consistency.

If the plane of the irons sits lower than the optic's reticle/dot, it's typically referred to as "lower 1/3 co-witness", as the irons sit in the lower third of the optic window. Some prefer this set-up as the irons don't obscure as much of the sight picture that way, which is especially useful on rifles with FSBs / fixed irons.
This is usually accomplished with a higher optic mount and/or riser.

[Hammer 35]

I like using an absolute co-witness when possible. It's really handy to be able to verify your optic maintained is zero after a bump by just seeing that it lines up with the irons. Or if you like switching optics alot, it saves having to zero them when going back to a red dot.