Larger of the two is is 50x42x15mm and weighs about 28g with 500mAh battery, other is 53x29x20mm and weighs 43g with 600mAh.
I suppose I should first explain GPS Tracking in general:
Small GPS Trackers designed to track kids or pets are typically less than 2" square. They require a GSM SIM Card, operate on 4G network, and usually use AT&T or T-Mobile. There are all kinds of SIM cards for Trackers and you can get one for as little as $15/yr that gives you 1Mb/mo which doesn't seem like a lot but typically these Trackers send out minimal data (Tracker ID, Date, Time, GPS Coordinates) and you can set the polling and upload intervals to infrequent (like upload 2 positions every 10 minutes). US Mobile has a 100MB and 40 SMS messages per month plan for $5.50 which is one of the best prices I could find currently.
These come with access to a website that will give you the Tracker's position (and historical track) that is free to use. The issue here is that you must fly in an area that has cellular coverage in order for the Tracker to report to the server and for you to run the app to see the Tracker's position on a map. I believe you can also send an SMS text to the Tracker and it will reply with a Lat/Lon msg so you wouldn't need a data connection on your phone (something I'm still trying to figure out with the Chinese). With GPS coordinates you could plug them into a handheld GPS receiver and navigate to the location, or use Google Maps which comes up from the Tracker App to show your location and Tracker location to navigate to it.
If you are flying a lot and under Part 107 then it would make sense to get a higher volume data plan. If you fly maybe an hour a week then you might be able to get by with the 1Mb/mo plan. Speedtalk has a $5/mo plan that gives you any combination of calls, text, or Mb data at $.02 ea (uses T-Mobile network). I have Tracfone Family Data plan and added an extra SIM for $6/mo which is 500 calls/text/Mb Data and it rolls over monthly with auto-refill.
I also use a Tile Pro mounted on the very front on top (with room behind it for the Tracker) using 3M Dual Lock (same stuff used to mount EZ Pass Transponders) which is better than velcro. I can pick up the Tile about 250 ft away and send a signal for it to start beeping (plays a tune) to find it. Tracker position should get you close enough for the Tile to be heard, although one Tracker has a beeper you can activate when close so you wouldn't need the Tile. Everything depends on where Drone ended up, time of day, use of anti-collision lights, etc. to determine your chances of locating it after it Houdini'd on you.
Feel free to ask questions or make suggestions as I am still in the development stage of determining the best Tracker, App, and Data Plan to meet the needs of Drone Pilots.
Update: My plan is to set up a Server in the US running Traccar which will replace the Manufacturer's Tracking Server in China. Has a Web Browser interface as well as Mobile Apps for Android and iOS. Configuring the Tracker is done via SMS messages to the number assigned to the Tracker when you activate the SIM card, and I provide a text file where you can copy/paste the commands into your Messenger app.