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What are the sizes of planning magnetic discs?

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Depth and diameter of a skittle planning magnetic disc Planning magnetic discs are measured diameter x depth. The diameter of a planning magnetic disc includes the measurement of the casing as well as the basic magnetic disc inside. The depth, however, is the distance between the top of the magnet’s casing and the base of the basic magnetic disc inside.

Flat planning magnetic discs

Flat planning magnetic disc diameter 20mm 30mm and 40mm A flat planning magnet has a diameter of either 20mm (0.79″), 30mm (1.18″) or 40mm (1.57″). The larger the diameter of the flat planning magnetic disc, the greater surface area of magnet there will be to hold the pieces of paper up. This is because the magnet will be able to have a better grip on the piece of paper due to its increased circumference, rather than an increase in its magnetic pull.
Flat planning magnetic disc height 7.5mm and 11mm The depth of flat planning magnetic discs can range from 7.5mm (0.3″) to 11mm (0.4″).
Stack of paper They can hold from 2 sheets to 20 sheets of A4 80gsm paper.
Wonkee Donkee says "80gsm stands for 80 grams per square meter of paper. It is also the standard thickness of a piece of A4 paper"

Skittle planning magnetic discs

Skittle planning magnetic disc diameter 12mm and 19mm Skittle planning magnets can either have a diameter of 12mm (0.47″) or 19mm (0.75″). The larger the diameter of the skittle planning magnetic disc, the greater surface area of magnet there will be to hold the pieces of paper up.
Stack of paper This means that a skittle planning magnetic disc with a large diameter will be better suited to holding larger sheets of paper onto a ferromagnetic surface.
skittle planning magnetic disc height 19.71mm and 30mm The depth of skittle planning magnetic discs ranges from 19.71mm (0.78″) to 30mm (1.18″). The taller the skittle magnetic disc is, the more pronounced the skittle shape becomes. This is beneficial to those users who are using the skittle magnetic discs to hang keys from, for example, as the more pronounced the shape is, the easier it is to hold things.
Stack of paper Skittle magnetic discs can hold a maximum of 12 to 26 sheets of 80gsm paper.

Map pin planning magnetic discs

Map pin planning magnetic disc 15mm diameter and 16mm height A map pin planning magnet is only available in one size: 15mm  x  16mm (0.59″ x 0.63″) and can hold a maximum of 13 sheets of 80gsm paper.

Hook planning magnetic discs

Hook planning magnetic disc 12mm diameter and 20mm height A hook planning magnet is only available in one size: 12mm  x  20mm (0.47″ x 0.79″) with a magnetic pull of 1kg (2.2lb). The hook planning magnetic discs are the strongest variety of planning magnetic disc as they can hold the equivalent of up to 100 sheets of 80gsm paper.
Wonkee Donkee says "The magnetic pull is the maximum weight of ferromagnetic material the magnetic disc can hold"