Help with bulkheads

[Chihuahua6]

The return holes that are drilled in my tank come through the overflow. They're 1.25" on the inside but slightly under 1" on the outside, meaning the acrylic is thinned out to make the inside have a different sized fitting. It looks like the hole itself is threaded too.

I think the previous owner had lockline coming out of the return. I am completely clueless as to what I need to order. Please help.

[jh2pizza]

I am lost without pictures of what exactly you talking about.

[Chihuahua6]

I don't know how I can get a picture of the inside of the overflow. Basically the hole is 7/8" and threaded. I think the inside is just routed to make the fitting flush.

Basically I need to know how to attach lockline to a 7/8" threaded hole.

[NanoReefWanabe]

sounds like it was drilled for a flush mounted 1/2" bulk head...

how thick is the acrylic? can you get to it with a dremel or a drill? you can make the hole how ever big you need to then...