375: Can you guess what it is yet?

I got a lens inverter thingy ring off eBay, and it produces a very narrow DoF. Guess what this is? It's on the theme of exercise...

Today I spent the day at MIRA, a testing ground. We were there in what will soon be the Jaguar CX-16 on the wet handling ring and straight line wet grip, and I learnt to drift a car around on a low friction surface! It was amazing fun, and we were sharing the proving ground with the Aston Martin Le Mans race team AND a race spec McLaren MP4-12C...great day!