Alternative insert for spacers by Transmit1

Hi, this is just modified insert for the great [Gravitrax spacer](https://www.thingiverse.com/thing:3325291) by [Transmit1](https://www.thingiverse.com/transmit1/designs). These have narrowed lower part so fit more losely to the base.

I created these, since the original was too tough. Putting it into plastic parts was OK, but putting into paper foundation was too tough, so I narrowed them by 0.2 mm from each side. The part that connects to the "Sternkreuzung" remains the same. Also, all other parts remain, so please go to the [original model](https://www.thingiverse.com/thing:3325291) to download.

If someone needs, here it is.