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Added at the request of a user a thicker and even more resistant version. The top and bottom walls have been increased to 2mm and the threads have been reinforced. (The initial profile is perfectly valid and resistant but this version is even stronger).
New STL (v2) also uploaded

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Support to add weight in the center of the JAYO cardboard spools (54mm internal diameter) and not have problems with AMS.

You can buy the screws and nuts at your hardware store for very little money, no special type of steel is necessary. It is something safe, it does not stain, it does not spill as may be the case with other adapters with sand, batteries...

Interior with 3 holes to accommodate M10 screws with nuts. In this case, using an m10x50mm screw and 6 nuts, we have a weight of 330g (3x110gr) with the metal alone. The total weight with the model and the empty coil is 400g. This weight is ideal for coils with less than 40% capacity, since this way they will always be between a minimum weight of 400g - 1kg, making the AMS work perfectly.

V1 vs V2: