@redkingjoe : Recently, there is no many new Pk-sized shell earbuds release. I can think of only 'VE Zen Lite (diameter 16.2mm as same as PK-sized)' that is included when you buy VE RA Amplifiers. However I never tried Zen 2.0 (diameter 16.9mm MX500-sized shell) and other cables version e.g. Oyaide 4n silver, Cardass Litz. In VE closed group, some said Zen Lite is nearly same Zen 2.0 sound with just minor downgrade cause 'Lite' has a smaller-sized driver. I am not confident enough that Kinera buds (which now already out of stock and Kinera say it will not further produce more) is beyond Shozy BK in every aspects since I ever tried Shozy BK just 5 minutes with full stock sponges. Within that 5 minutes, I personally prefer Kinera buds over Shozy BK. Penon BS1 shell size is nearly similar to MX500 shell size. Perhaps a bit 0.1mm smaller than MX500. If shell size is your very first priority concern, I don't recommend it. Even a new released astrotec LYRA collection earbud is around MX500 shell size or might bigger and heavier.. In PK-sized shell category, we have very few choice.
Update : I forget K's earphone brand. They just released 2 their new Flagship earbuds.
1)
Poseidon (海神) 457$, Silver housing, 215Ohm, N55 magnet strength (more than 1.3 Tesla), driver diameter 14.6 mm., front cover diameter 16.2 mm., mmcx detachable cable
2)
Ling (铃) 229$, Brass housing, 195Ohm, N52 magnet strength (more than 1 Tesla), driver diameter 14.5 mm., front cover diameter 16.1 mm.