PAC-12 JPC-12 7-50MHz Portable HF Antenna
I bought this antenna because it appeared to be very well built, with very positive reviews on Aliexpress and YouTube. I also found that the spike system to hold it in place might be very interesting if stuck in the wet sand of a beach. The loading coil can also be bought separately, which can be a good option for those who already have an M10-threaded whip. José López from Puerto Rico (NP4VO) has tested this antenna in its original configuration for Beaches On The Air.
I have also tested three of the four sections provided to extend my ANT-129 military whip on my radio trolley, and it worked very well (see the videos attached). At home I also tested the loading coil with the telescopic whip provided, and whereas the loading coil looks and works awsome, the telescopic whip looks flimsy to me, at least as compared to a true military whip, so I wouldn't personally recommend it for portable use.
All in all, even if you already own an M10 whip, I think it is worth buying the whole set rather than the loading coil alone, because it also includes four extension sections, the ground spike, the base, and a nylon bag of the highest quality. Even the telescopic whip can be useful to play with at home. Highly recommended!