A few months back Tile updated their offerings with the Tile Slim, which was a vast improvement over the original Tile, but not meant to entirely replace its predecessor.
The Tile Slim was meant to be placed in a wallet, stuck to a tablet/laptop, or somewhere that you wanted a thin discrete way to track belongings. The Slim was not able to be (easily) used with car keys, since it lacked the keying hole.
Fast forward to October and we now have the "Tile Mate".
The Mate is a replacement for the original Tile, coming in at 25% smaller, while packing all the same features. Including the key ring hole.
The Tile Mate is also part of the reTile program, which allows you to easily replace your tile when the battery runs out. Tile generally says a Tile should last about 1 year, but your mileage may vary.
The Tile Mate can be purchased directly from the Tile website for $25 each or $70 for a 4-pack.