The Donnas have always been a better gimmick than a band. When they broke onto the scene, they had all kinds of Spin-worthy selling points: they were teenage girls still in high school; they all wore the same t-shirts, emblazoned in busty 3-D with their "Donna initials"; and they played music that was always able to be succinctly summarized as "band x meets band y." People fawned over the Donnas' image more than the music the girls produced-- and by all rights, they should have become bigger than they have, based on America's love affair with style-over-substance.

Most people overlooked the best thing about the group, though: they successfully appropriated the sounds of the testosterone club. Not exactly like the riot grrls, who famously hijacked the attitude of boys-only punk, but in their own more invasive way. The Donnas were like geologists exploring the deepest strata of hard, heavy rock, and forcibly carved their niche out of granite-sized preconception and prejudice in that gender-imbalanced world.

People-- especially music journalists-- seemed to forget that the Donnas' initial Ramones-clones sound gradually yielded in favor of 70s and 80s metal plagiarism. Each release inched them further away from the fun three-chord punk spirit that made such an initial impact. And now, with the arrival of this year's Turn 21, their fourth full-length, The Donnas have become the male nurses of American beer-fueled heavy metal, in danger of digging their own rut so deep that they won't even be able to peer over the edge, let alone ever escape it.

Every song drips with bawdy attempts at sexual promiscuity. But just Vince Neil screaming "girls, girls, girls" and name-checking strip bars is unlikely to whip a woman into a frenzy of amour, The Donnas attempt to titillate and fail miserably. Lines like, "You pulled me over and I pulled you in/ C'mon, officer, let's go for a spin," from "Police Blitz", and the blunt metaphor, "Let's play ball, we don't need a court/ Just you and me, baby, full-contact sport," in "Play My Game" feature all the eroticism of The All-New Three's a Crowd with Alan Thicke. The Donnas are boring for the same reason pornography is: a boggling lack of subtlety mixed with crudeness.

"Little Boy" is the most enjoyable track, mainly because it has more of an early Donnas sound, and because the lyrics are funny in that bad-sitcom kind of way. Evidence: "Have you ever even tried to use a comb/ I think you might be missing a chromosome/ 'Cause you keep coming back for more." The only other song worth a mention is the first single, "40 Boys in 40 Nights", which sounds like Kiss at their best (but still Kiss, y'know). Its melody dives and surfaces, and the diesel-chug of the guitars bursts into riff-as-punctuation at just the right times. The lyrics are right in line with the rest of the album: "Spendin' every night in a different state/ Spendin' every night with a different date."

In keeping with their trend of covering a metal classic, the girls turn in a perfectly humdrum treatment of Judas Priest's "Living after Midnight". Without improving or reinventing it, there remains little reason to even include it, other than to give the listener a glimpse of their influences and favorites. Really, girls, there was no need to tell us-- it couldn't be more obvious. As for the rest of the disc, try not to get lost in the crowd. It would be futile to attempt identifying the low points, as each same-sounding song after song is as forgettable as it is mediocre.

The biggest disappointment is that the title implied we were going to get older, wiser Donnas. For a young adult, turning 21 is a milestone; a time when their perspective on life changes, and society has no choice but to finally regard them as an adult. I may have held out a little glimmer of hope that The Donnas' Turn 21 was going to be a similar landmark turning point in their maturation as a band. But not everyone who turns 21 is the beneficiary of a sudden boost of the maturity hormone, and The Donnas are still playing some pretty juvenile rock 'n' roll.