What is the difference between the adhesive and magnetic versions?

The adhesive version sticks permanently to a phone or case. The magnetic version attaches to a MagSafe case and can be removed and repositioned.

Will the magnetic version work on any phone?

No. The magnetic backing needs a MagSafe-compatible case. On a plain case or a bare phone it will not hold.

It is 60mm across, roughly the width of a few fingers, so it sits small on the back of a phone.

No. It is a grip for holding the phone, not a kickstand or a card holder.

Soft PVC, the same rubbery plastic used for many novelty phone accessories.

Not reliably. The adhesive is meant for one placement, so a second stick usually holds poorly.

At MarDeLunaArts, for $13.00, as of our latest check.

2 stores we checked sell it, including MarDeLunaArts, Amazon.

$13.00at MarDeLunaArtsChecked Nov 12

Compared across 2 stores. Prices are checked against each store and labelled with when.

It checks today's price at every store, compares the alternatives and answers in about a minute.