Summary

This is a mod of fischertechnik part 37 468 (Baustein 7.5) with hole.
It is basically a 7.5mm thick block with a hole for an axle.
Fischertechnik blocks with hole have thickness of either 15mm or much smaller than 7.5mm.

The other part is an adapter to connect such blocks.

Another compatible 4-sided adapter with hole is here:
https://www.thingiverse.com/thing:2820890

Print Settings

Printer Brand:

Anycubic

                                            <p class="detail-setting printer"><strong>Printer: </strong>                     <div><p>i3 Mega</p></div></p>                                                                                <p class="detail-setting rafts"><strong>Rafts: </strong>                     <div><p>No</p></div></p>                                                                                <p class="detail-setting supports"><strong>Supports: </strong>                     <div><p>No</p></div></p>                                                                                <p class="detail-setting resolution"><strong>Resolution: </strong>                     <div><p>0.1mm</p></div></p>                                                                                <p class="detail-setting infill"><strong>Infill: </strong>                     <div><p>50%</p></div></p>                                                    <strong>Filament:</strong> MATERIAL4PRINT PLA                dark grey                    <br>                        <p class="detail-setting notes"><strong>Notes: </strong>                    </p><div><p>1.75mm</p></div>

Post-Printing

Re-drill holes with 4mm

How I Designed This

This is a FreeCAD design

fischertechnik block 15x15x7.5 with hole and adapter