[NTG-context] Left + right justification at once.

Hi all, Am using \vbox{\hsize8cm text} to typeset my document with blocks of text. This makes a left and right justification of the text, but most of the time it does work alright and i get a ragged right text. What do i have to do in order to avoid this and get my text justified at both sides ? Thanks for any help. Dirar