This adapter will correct the one-way interchange between a male 5.5x2.1mm (like those of the ATM and most desktop vapes) and a 5.5x2.5mm Female DC jack (like those on the Collyland products).
A female 5.5x.2.5mm jack has a larger 2.5mm post and is not backwards compatible with 2.1mm socket in the tip of a male 5.5x2.1mm plug. This adapter allows you to use your existing ATM hardware on 5.5x2.5mm female DC jacks.
Priced each.