The tips on the bold are oval. The widest on the X Axis pictured in yellow is 4.7mm, the tallest on the Y axis is 6.9mm.
The way the bud is angled means it sits neatly at the angle it needs to further back within your ear to maximise the microphone usability, given its an outside mic that isn't on the end of a stem, send sound waves in the natural direction through the ear canal and not put pressure on your concha.
It means I have to use smaller tips on these than I would other earbuds that sit further back, and can't use foam tips as that would be uncomfortable - it's the total opposite design to the likes of the tozo nc9 or Spunky beats which squeeze into your concha. At first I thought what the hell are they doing?! None of my foam tips fit. Then I found foam tips that did fit, but they sounded worse.
Once I got the loupe out and saw the oval I figured out why they had designed them this way and went back to using the stock medium tips, and they are perfect. It makes them really comfortable for all day use and is a little design feature that differentiates them from the rest of the chifi crowd, as the only other buds I've seen use this design are Klipsch and I think it was Panasonic IIRC. It's a brave move by Tronsmart but there is reasoning behind it and it works well for me at least. Just don't try shoving these things into your ear canal as even if it is wide enough, it will be uncomfortable both ergonomically and audibly. Also, without the right tips, I suspect the sound bouncing around the pinnae is causing the reports of over-heavy bass.
