These specially designed Peak directional caps have a small hole angled to direct the air to the very bottom of the sidewall as well as the bottom of the insert. This helps address one of the biggest issues with the peak, especially if you use a smooth surface insert like quartz or Ruby, oil creeps up the side walls, away from the heat! I find the stock cap and most bubble caps tend to make this issue worse since they only direct air at the bottom. Being able to push the oil down off of the side wall with the cap provides a much bigger hit. Plus that little hole means they are a little restrictive which pairs perfectly with the Peak! That’s the reason this is the cap I keep coming back to, no matter how many I purchase. The BEST functioning carb I have found for the peak! USA made colored borosilicate directional caps made by artist Bandito Glass. Colors and caps are first come first serve, but if there is something you really want I can definitely get it for you.
I use mine all the time, go check my IG feed to see it in action!