"that kind of a thing"

by Mark Israel
     [This is a fast-access FAQ excerpt.]
The forms you're likely to encounter, in roughly decreasing
order of formality, are "that kind of thing", "those kinds of
things", "those kind of things", and "that kind of a thing".  Sir
Ernest Gowers wrote:  "it is as well to humour the purists by
writing things of that kind."