t ring to focuser

[ridla1984]

I have a 90mm refractor and just got a t ring, my barlow acts as the t adaptor but just noticed the t ring also screws directly on to the scopes focuser. My question is does this remove the need for the adaptor or is there another benefit to the few cms of extra length the adaptor gives?

[m.tweedy]

It depends whether you can achieve focus without the extension.