Pipe fitting dimensions

[PlumbHum]

Hello,
does the x-dimension for copper ALSO include plastic push-fit, OR is this known as the y-dimension?
ALSO, why (on a previous post) is the internal pipe fitting for LCS, 13mm; is this z-dimension standard or does it change on whether black- or white-heart fittings are used.
I haven't had that much experience measuring or cutting LCS and just wondered?
Many thanks for your time & patience, slainte!

 

[on31ll]

I dont know the dimension exactly for plastic but cut pipe on the line printe on the side then insert it then demount the fittin and measure the depth !

Why do you need to know this ? Sounds like im being funny but im not