Don't want to go on onshape and figure out what config you need, here is a pre exported version of the most popular configuration of opinsert, along with a bill of materials for everything you need.
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BOM (per insert):
1x m3 30mm SHCS
1x m3 lock nut
1x m3 v-groove pulley (3x12x4)
(if using Misumi sar 2xx, use Misumi tsar 4-12 for screwing the slides together)
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Recommended print settings are: PETG or ABS, .2mm layer height, 4 top and bottom layers, 3 side layers, 40% infill.
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If you want to use other configurations of this design, go to https://cad.onshape.com/documents/4f3446e64b18f76af4773a36/w/84d84ca5d4800093934b8589/e/7adfb8c1449541a132fe5a9c
The author marked this model as their own original creation.