It is used for middle school physics mechanical demonstration and student experiment in group, with main dimension of hook code: outside diameter 31mm, height 34mm, and it consists of 200g*4 hook code.
....It is used for middle school physics mechanical demonstration and student experiment in group, with main dimension of hook code: outside diameter 26mm, height 14mm, and it consists of 50g*10 hook code.
....It is used for middle school physics mechanical demonstration and student experiment in group, consists of 10g*1, 20g*2, 50g*2 and 200g*2 hook code.
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