I use a FX "brick".
Ie; their earlier version. Works a tad different vs most other chronos in that it´s a doppler radar.

Very small, very compact. Runs on 3 AAA batteries. It´s just a transmitter though why you hook it to your smartphone via FX app, and the whole thing works a million bux.
Doesn´t care what weather.. temperature and so on. It being a doppler in turn, it just plain works.

Sensivity of the unit can be set through the app on the phone, as can pill weight, caliber and what not. Mind you, this is the FIRST version of it.

The second one just hit the market and them are more expensive and see.. here´s the thing. I place mine close to the muzzle. On a bench, a stick.. whatever. I NEVER EVER hang anything what so ever to the barrel... Again, the unit just simply works. No "dialing in" or the likes.

Turn it on. Open the app on the phone and the two asks if they should dock right off. Just press yes, and the unit in essence does the rest. You pick if you want to add pill weight and through that get muzzle energy together with speed.
You can opt if you want the app to read it out loud to you.

Here´s what i think..
They´ve become rather common why i say, find a used one. I did, mines a few yrs old by now, and i believe i forked over the equivalent of approx 60£ for it. I´ve used the living SNOT out of it, not only airguns but loads n loads of blackpowder firearms too.

It in my opinion only got one drawback and that´s that it´s "power hungry". Thus i normally pick AAA batteries up in bulk, and if i´m at the shop.. recharge AAA´s.. Thus not an issue really.

I believe it should be noted that i also own, and use of course, a rather expensive LabRadar. Yep, that orange doo-hickey everyone and their uncle raved about a few years back.
FX and Garmin have both released their take on the LabRadar semi recently, but to be quite candid i´ve looked into both and albeit the Garmin size wise is about on par more with the FX brick i still don´t see any "need" to replace my trusted old LabRadar.

Btw. To trigger the LabRadar using airguns i´ve got one of their small microphones that handles that.. just point towards the gun and set sensivity..

This has of course also lent that i´ve come to compare the two and truth be told the difference is like 1 or 2 fps or thereabouts. In other words.. same same from a practical point of view.

The LabRadar though also hands that it "tracks" the projectile which hands that i can calculate BC for basically any given projectile too. Needed? To most.. not really to be honest. To a nerd like me though, yes

LabRadar though (bought that used too) ran me an easy 10 times the money of the FX brick.

The "brick" however is what by FAR gets used the most. As it´s always there, you can place it like.. where ever.. Sturdy and so on.

One note though.
I keep a tiled floor at the shop right why it´s been more than once the damn thing has hit the floor. At first it had me running around like a one legged chicken as it had dropped to the floor and stopped working!!
GAAAH!

Well. Took it apart, and within there´s a joint where the one part of it hooks to the other aaaaaand.. them had just come apart. So.. just pushed that back in and bolted the thing back together. Yep.
Back in business.

So. Seeing the alternatives, nope. The original "brick" is in my book hard to beat.