A Most of the market are 45# steel, it can also meet your basic use requirements, but over time, the screw that fixes the tool may have the problem of deformation, because the hardness is not enough, so we manufactured the stainless steel material, it is harder than the 45# steel material, the service life is longer. Q How do I choose them?A If you use it less often, you can choose 45# steel, if you use it more often it is recommended to choose stainless steel, it can accompany you for a longer time. This item is in the category "Business & Industrial\CNC, Metalworking & Manufacturing\Workholding & Toolholding\Toolholding\Quick Change Tool Post". The seller is "anruimachine" and is located in this country: CN. This item can be shipped to United States, United Kingdom, Mexico, Germany, Japan, France, Australia.