Fitbit said there would be more Fitbits before the end of the year. Now we know there are at least two more.

Today, Fitbit unveiled the new Charge 2 and Flex 2 activity-tracking wristbands, adding incremental updates to the wristbands in a way that strategically differentiates them from the existing Fitbits on the market. All the details about the Charge 2 are here; for more information about the new Flex 2, read on.

The Flex 2 is a slim, simple activity tracker that, like its predecessor, tracks steps, distance traveled, calories burned, and sleep. It doesn't have a display; instead it uses five tiny LED lights to tell you how far along you are in your daily step count, signal when you've reached an activity goal, or alert you to smartphone notifications. It also doesn't have optical heart rate sensors, or (not surprisingly) GPS.

It does, however, have Fitbit's Smart Track feature, which means it automatically recognizes when you've started certain exercise activities. It will vibrate when you've been sedentary for too long. Maybe most notably, it's also "swimproof," making it Fitbit's first waterproof activity tracker (up to 50 meters), and it will automatically recognize when you're swimming. Expected battery life is around five days.

In short, the $99 Flex 2 isn't vastly different from the previous model, or even that different from simple wristbands made by competitors. But for some people, the brand "Fitbit" alone will hold some weight.

Fitbit, which leads the US market in activity trackers, sells seven different devices now (an unchanged number, since the Flex 2 and new Charge 2 are effectively replacing their predecessors). The company lumps them into three categories: everyday activity trackers like the Flex 2; trackers for more active people, like the Charge 2 and Blaze; and the performance-focused, GPS-equipped Surge.

The product lineup can be overwhelming even or confusing for people who just want a basic step-counting wrist thingy, but Fitbit's strategy isn't unlike other wearable makers, from Fossil-owned Misfit to Garmin: let's just throw a bunch of wearables out there so there's something for everyone.

This one is really meant for two types of buyers: those who really want something simple, discreet, and waterproof; or those who wear a serious performance tracker during workouts but then want to supplement that tracker with an everyday step / sleep counter. Since Fitbit's app now supports multiple Fitbit devices, this is an option with something like the Flex 2.

The Flex 2, which is actually a small module that pops out of its flexible wristband, can also be worn in an accessory bracelet like the one pictured below. Fitbit sells three of these, in gold, silver, and 22-carat rose gold.

You'll still have to wait a bit for the Flex 2, though: while it's available for preorder today, it won't ship until sometime in early October.