Replacement HSS top front knife for Muller Martini 360 361 390 370 380 400 459 book trimmers. We offer the best quality cutter knives for these cutters in several styles / locations, including these top front and top side knives for the left and right sides. This particular knife has a bi-metallic composition consisting of one part 18% T1 German Tungsten High Speed Steel and one part standard grade steel. A special fusion process bonds these two grades of steel together to produce an extremely wear-resistant knife. Expect three to five times the life of conventional blades. This type of high quality knife is used solely in bed knives for three knife trimmers. These Jayhawk Diamond Cut blades are manufactured to not just meet, but to exceed OEM specifications, ensuring extreme precision and longevity.