Man I wish these came out in Australia
I use poly. My favorite is OTS normal.
I use cotton on all Duncan fixies and the same thing happens to me, especially with the old Imperials and Professionals in my collection. Poly doesnāt āgripā the axle the way cotton does when string torsion is high, and so doesnāt produce the kind of tug response I like (akin to loopers). But that tight grip on the axle also means that cotton is going to get eaten through much faster than poly. You have to pick your poison, I suppose.
Nothing like throwing a breakaway and having it actually break away.
And that is precisely what happened.
some butterfly axles are sketchy and cut strings quicker. iāve been disassembling to make them prettier and polishing the axles, no cut strings/quick breaks after that. poly or cotton.
Iām scared to pull mine apart.
Edit: @Sleeper80 was it you that was cracking butterflies open and modding them a bit with metal washers and such? I would be interested in concurring my fear of opening one up and trying to make it better.
yeah here is my mod thread: Sleeper80's Butterfied Butterfly Mods
this should at least help you with how to disassembleā¦
I recommend getting a bunch of butterflyās to experiment with since the price is fairly low for modding. You may end up with less yoyos than you started with and a few in parts or broken, but its a fun project.
Latest mods: easter bodies with glitter bombed translucent caps. I made concave axles and put a high polish on them.
Wow those look pretty. Thanks for the link, Iāll delve into it later today!
Cool listing I found in case anyone is interested:
Copped the new version of butterfly in my local toys r us today, they only sold a few assorted units atm but Iām stoked to play with the fixies with the cotton nylon string later.
Not sure if itās just the lighting but is that a pink Imperial? 
Also, which mall? 
Robinsons galleria cebu 2nd floor, I just made a quick visit at toys r us for a minute to see if they have new restocks of wfm gunplas after I brought some groceries until I saw a few duncan yoyos in the front of cash register.
Brought the green BT ones since its the last one they have
its a purple pinkish color
Alas, thatās ~870 km too far. 
Oohh, thought those were only found at Target. I wonder if the butterflies made it too. Iāll keep an eye out.
I reckon its available on your nearest toys r us for sure, Iām planning on checking out on ayala mall after the holy week ends see if they also restoked in different duncan yoyos.
I believe the pink Imperial is part of the standard colors, the pink Butterfly was only a Target exclusive for the holidays