Lots of choice. Vents, aero, MIPS? I have a Giro shaped head, which means I wear Medium Giro helmets. Have an Air Attack which is aero, odd-looking, fast and amazingly comfortable. I had a Giro prolight until recently that was unbelievably light, and when called upon, smashed when I struck the back of my head on the tarmac in a practice race. I replaced it with an Atmos in black fluro.
The most important part is that my head is giro-shaped, not Kask-shaped. I found Kask helmets to be beautifully made, but dug into the back of my head.
So try a few brands, they do differ. Pick a brand that fits and a price to taste. I rather like the fluro colored helmets, as I think this adds a little visibility during daylight. Spend £60-80 for a nice one.
