I bought one of these a few years ago (outside of drop.com) just to get the adapters, don't even have IEMs with MMCX connectors. The adapters themselves are fantastic, use them all the time. Between 2.5mm (original cable), 3.5mm single-ended, 4.4mm and 3.5mm balanced you can connect to pretty much anything, especially if you throw in the drop 2.5mm to XLR adapter. So glad they also included 3.5mm balanced too with I can use with my Plenue S.
Anyway, I paid $100 USD and have got great use out of them, wish I could have got them for $50!