The dimension of the flat holes of the four-arm spiders is designed according to the M18 screw.When the installed screw to the flat holes is less than M18,the axial load of the routel will transfer from the offset washer to the spider.It can be seen from the test ,when the axial laod is less than 3500N,the offset washer can totally meet the requirements of the stress.In addition,the original design of the flat holes of the single arm,two-arm,three-arm spider has been cancelled.The needed bearing of the holes should also be transfered from the offset washer. If three-arm spider are needed,customers should add the number of arms in the end of the code such as:the code of three-arm