Shimano Shifters SL-M315 Altus

These are the simplest levers for indexed (clicky) gears on a flat-handlebar bike. They're as durable and straightforward as you'd expect from a Shimano product that's been around for this long, and we must have installed thousands on bicycles. The gear window is on the bottom, sometimes that's useful to know if your bars have really tight curves.

If you're replacing SL-M310 parts, these are the same. They didn't used to make a 2-speed left, but now you can match your front gears, too.

You'll need to match the number of gears on your cassette to the number of clicks on the shifter, but you can use any SIS-compatible 7-speed or 8-speed derailer, and most Shimano 9-speed derailers, too.