the early 7400s had thick springs in the calipers and none in the levers , as well as pressed alloy pad holders . the later ones were " SLR = Shimano Linear Response " with thinner springs in the calipers and small springs in the levers too , they also had the smooth "shark fin" pad holders , which your set on the left has . the pad set on the right caliper are Shimano 600sfoz":1mnyld48 said:Allen key. And they're 7402, not 7400. I'm not sure what the difference is between the two, if any?