-Filament of your choosing (The example shown in the photographs I have provided is printed in ColorFabb PLA/PHA 'Sky Blue' filament). -4 Springs . As a guide the specifications of the springs I use within the design are as follows: Uncompressed Spring Length (mm) - 23 Wire Thickness (mm) - 1 Inside Diameter (mm) - 17 Outside Diameter - (mm) - 19 PRESSURE At 50% Compression (Grams) - 350 When creating an extended base version of the coin holder I use 8 such springs and superglue them together in pairs to create 4 longer springs. I find Loctite 'Power Easy Gel' to be very effective for gluing the springs as it is less runny that most glues and it stays on the springs long enough to create a strong bond.