Scammers
Even if the app is fine they have malicious intent to charge users, while I understand that they want to monetise their efforts, this is a scammy way to do so. Avoid downloading.
Not enough ratings yet to assess Ring Sizer.
Ring Sizer: Measuring Tool App appears legitimate, with a few gaps. AppsHunter Legitimacy Score for Ring Sizer is 75/100.
Based on 75 of 100 points across 7 verification signals from App Store and developer data.