Harry Potter Solemnly Swear Womens' Cut-Off Sleeve Muscle Juniors Tee T-Shirt. This muscle tank is a great gift for any Harry Potter Fan. With the iconic saying that would open the Marauders Map in which on a black Tank Top it is a fun fashionable statement of your fandom. This shirt is listed in Juniors sizing which is smaller than womens, for fuller figures or if you prefer a looser fit, we recommend sizing up. This is both a fashionable Tee Tank as well as comfortable enough to lounge in.