Mayday: Deck Protectors: Card Game Premium Sleeves 63.5 x 88mm (50)

 Yes these are "Standard" size card sleeves.  They are specifically designed to fit 63.5 X 88 MM cards but the external dimensions of the sleeves are commonly referred to at 66x91 MM.  It doesn't make any sense why these are the only cards referred to by both their internal and external dimensions but if you're looking for sleeves that are 66 x 91 MM, you've come to the right place.  These are the most common sleeve size BY FAR in the industry, the MTG sized sleeves.