Modern tenkara rods are long, light, telescopic rods that are ideal for fishing in small streams and pocket water. The line is tied to the rod tip, so the rods have neither reel seat nor guides. It may take a while to get used to, but not having a reel and guides is an advantage, not a disadvantage, when fishing small streams.
Without guides, the rods can collapse into the grip section, making them extremely portable (and much easier to carry on a stream side trail). Without the weight and bulk of a reel, the rods are very convenient for backpacking.
The purpose of a reel is to hold extra line, so you can make long casts and so a fish can
make long runs. In the smaller streams where tenkara really shines,
you don't make long casts and the fish don't make long runs. You
don't need extra line and thus you don't need the reel.
Of course, without a reel, a fish cannot take line, so there is a limit
to how large a fish you can catch. That limit is much larger than you
would expect, though. Trout well over 20" have been caught with tenkara but just like ultralight spinning rods, tenkara rods were not designed for really big fish.
The fish that Japanese tenkara anglers catch are generally around 8-10" although any of the rods offered on Finesse-Fishing.com can handle fish larger than that. The manufacturer's maximum tippet recommendation will determine what you can catch.
In the last few years, a number of American tenkara companies have started up. Most sell inexpensive rods made in China, often from the same factories, occasionally even the same rods with different paint jobs. A few of the big name American brands are sold in stores, but just because they are well known or readily available does not mean they are the best quality. Truly, they just aren't the same as the top Japanese rods. Finesse-Fishing.com sells only rods made for the Japanese domestic market.
The following companies make excellent quality rods for the Japanese domestic market. (They also make low end rods, which are best left in Japan. Like everything else in life, you pay for what you get. If you want to get high quality, it will come with a high price.)