Sonic difference Mullard

Hello friends
I am using a pair of Mullards 12 AX7 long plates with round getters.
Can you tell me the sonic difference between the round getter vs the square getters ?
Many thanks
The purpose of getters are to absorb gases that buildup inside the tube, after initial burn in, and over time.

That is their only effect on sound quality.
Don c55, thank you very much.