Page Hamilton, the band's founder and chief songwriter, is the only original member appearing on the album. Therefore, many purists object to it being called "Helmet" and consider it to be a Page Hamilton solo project. According to Hamilton, John Stanier (drums) and Henry Bogdan (bass) both declined the invitation to reunite.
Despite the purists' objections, the album carries on in the Helmet tradition with Hamilton's trademark staccato sound. The album was recorded as a three-piece with John Tempesta on drums and Chris Traynor (guitarist on the Aftertaste tour) on bass. After recording was done, bassist Frank Bello was brought in so Traynor could return to guitar.
The Japanese release has two additional tracks: "Black Light" and "Just Like Me." These tracks, as well as "Smart" (a.k.a. "Opportunity"), "Enemies," and "Unwound," were originally recorded as Gandhi tracks, Page Hamilton's previous band.
Upon release in 2004 the album received mixed reviews from critics, and alienated a portion of the bands fanbase. Pitchfork writer David Raposa gave the album a mixed review. He criticized the bands change in sound writing "Helmet attempt to diversify their portfolio, offering dynamics and approachable melodies and other types of listener-friendly capitulations one wouldn't associate with the folks that dropped Meantime and Unsung."
Johnny Loftus of Allmusic gave the album 3 stars and wrote in his review "Size Matters emphasizes for the bloated alt-metal elite what it means to have craft and a little self-control. It isn't necessarily memorable, but as an exercise in measured, even artistic rage, it's classic Hamilton."