filament leftover sample mag spool lightweight

I designed my own filament leftover spool.
The spool sticks together by mounting magnets (10x3mm).
outer diameter 150 mm
filament diameter 90 mm (like a normal spool for not stressing the filament leftover itself)
inner diameter 60 mm (for almost every spool carrier)
inner width 30 mm
outer width 36 mm (just half a normal 1 kg spool)

There are many 2,5 mm holes to stick in the filaments end while not using.
There is also one 2,5 mm hole for spooling filament onto this spool.

As shown on the pictures it is lightweight designed, it weight is about 88g without magnets in the single spool combination.

Mag spool A is the basic spool element
Mag spool B is the end spool element thick
Mag spool B2 is the end spool element thin
Mag spool A-B is a variant to stack more than one spool before mounting Mag spool B
Mag sppol B3 is another ending for the spool (19.02.2024)
Spuelenfueller_M8 has to be printed twotimes
M8_nutter_with_washer

a piece of M8 threaded rod about 80