Vibrators
My RFY items contain volumes of vibrators - all colours, shapes, sizes and functions including free hand, strap-on, in-situ wearable and remote control. I've even seen a Bluetooth one.
I have no idea why my RFY has any let alone so many.
I've never ordered one and my mind boggles to think how it would be possible to review one with relevant media.
I'm guessing a wave tank with ripple pattern analysis could be a way forward.