Hiwin guide rail bearing block HGH20CA installation help

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Thanks so far for your advices.
I have another issue with my profiled rails
On the rails i can recognize the following code HGR20H 301 8X-5c that i cant translate according the Hiwin guidway.
HG means HG series
R means that the rails are interchangeable( there is no master and subsidiary rail, both rails can be used the same)
20 is the thickness of the rail
H (that follows 20) must be the precision level of the rail I cant find out what the 301 8x-5c means. Does anybody have any idea?
Here the photos that i took
Thanks for your time
Vagelis