Replacement barrel question

Looking at replacing my original barrel but slightly confused.

Can I install any barrel and use my original t piece? Do all replacement barrels have the same outside diameter?

Just looking at replacing the barrel, O ring and spring.

The t-piece is glued to the barrel (if done right) and I doubt you will be able to dissolve/melt the glue off. All of my blasters from jinming came glued with araldite. I use waterproof silicone on my replacement barrels. But I bet silicone won’t last on a heavily modded blaster.