Bought at a store called Beauty First
It is a 1''/25mm
I paid $125 for it
you can get the same results with your regular curling iron.
I even made a video about it called "wavy hair with a revlon curling iron"
Here is how I do my hair! It is kinda hard to hear me in the video but my main points are:
-use different amounts of hair on each curl so that it looks messy and undone and more natural rather than uniform
-I don't wrap the ends around the barrel because I like how it looks with my ends strait
-i stop winding the hair at various points because I like how it gives it an "undone" look
-wait for your waves to cool before you break them apart
-use a salt spray or wave spray for beachy messy texture
oh, and the size of the barrel for my curling iron is 25mm/1 inch