I like the astro;
- it's m21x1 threaded; same as my vamo, zmax, king, and chiyou.
I got a 10pack of chiyou 510 steel topcaps and I leave topcaps permanently affixed to the toppers, so when I'm replacing toppers on one of my astros, I don't do wear and tear on the 510 connection.
- it's telescopic
- comes with a kick tube