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The locking mechanism has two parts
Standoff |  |
Screw |
 |
SX 4M2 has multiple key-hole shaped openings for supporting different M.2 sizes.
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Insert standoff in keyhole, groove down.
Push standoff to the narrow end of the keyhole.
Tip: If pushing the standoff in place is difficult, consider using a 4mm hex socket for pushing the standoff in place.
Install M.2 card in the M.2 slot and tighten the screw onto the standoff
Thermal coupling of SSD
Most of the power is generated in the flash controller which in nearly all NVME SSDs is located close to the M.2 edge connector, on the component side. A 0.5mm/1mm 20x20 mm positioned as depicted would be effective in keeping the NVME SSD cool.
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