How does an ordinary thing relate to its matter? lf they are identical, ordinary things cannot change their matter, and never persist as ordinary things for more than a moment. lf they are distinct, then every ordinary thing coincides with a second material thing, as "constitution" and temporal-parts views have it. Both alternatives presuppose that the matter of an ordinary thing is itself a concrete entity: a "mass of matter". This paper defends the view that there are no masses, but only particles.