Ok, here are four different square taper (cottterless) cranks I have to hand to allow some visual comparisons. I also weighed them myself as sets (i.e. combined weight of two cranks).
From left to right: SHW (Alu) 125/150mm = 355g, Nimbus Venture (Alu) 125mm = 388g, Qu-Ax (Alu) 125mm = 343g, Unbranded (steel) 125mm = 676g
Oh and here is a bonus picture of them mounted on my 24" URC unicycle
