at least 7. The reason is..

thin ones are more prone to dismatch when putting together.

所有跟帖： 

• “7” 指7mm ? 相当于多少mil 的啊？ -pickshell- ♀ (0 bytes) () 10/15/2023 postreply 07:58:21

• 1 mil = 0.001 inch -borisg- ♂ (0 bytes) () 10/15/2023 postreply 08:06:39

• 哦，按这个赶紧算算去：） -pickshell- ♀ (0 bytes) () 10/15/2023 postreply 08:19:37