I used a Titan brand 3/4" magnetic snap - and it is STRONG.
I found two people on Etsy that sells the slimline ones. I have a message in to the sellers asking if they are as strong as the regular magnetic snaps. I"ll let you all know as soon as I find out - hopefully the person will message back right away so I can order some before you all get to them first :lol:
Seriously though - I'll let you guys know as soon as I find out - but yeah, the snaps I used were 3/4" and they are potent.