Knog’s tagline for the Oi is: “Bike bells that don’t look like bike bells.” Pretty accurate, if you ask me. Instead of a dome, the Oi has a curved chunk of metal mounted, via springs, to a plastic clamp that gets beat upon by a plastic striker.
The are two sizes: small to fit 22.2 mm bars and large for bars between 23.8-31.8 mm. I tested a large and it works fine on 31.8 drop bars; smaller sizes will need to use the included shims. There are cable grooves molded into the clamp. This might sound minor, but it makes it much easier to mount the bell cleanly on road bikes with the cables under the bar tape.
The bell sounds great. Maybe not at loud as something like a Spurcycle bell, the Oi still gets plenty of attention on the bike path. I would never have guessed a bent bar of metal could sound so good, but I’ve been wrong before and will be wrong again.
If you are happy with your current bell, there probably isn’t much for you here. But if you are looking for a sleek bell that integrates smoothly with road bikes, this is the best thing going. For flat bar bikes, the small size should fit in well with sometimes-crowded real estate around the brake and shift levers. The Oi is a surprisingly innovative little device for a category as mature as bike bells. Four finishes are available: black, silver, copper and brass.