Stripes I & II are the names of Stocking's spiritual katanas. Stocking has the ability to transform her stockings into a pair of katanas, which can be used to battle ghosts. She first referred to them by name in "High School Nudical".
Stripes I & II can be attached at the base of the hilt, to attack in a similar way to how a helicopter's rotors work. Her katanas are able to hurt any spiritual being, such as angels, demons and ghosts.
Like any other sword, Stripes I & II must be sharpened, and if not properly cared for, can break. Stocking is also unable to transform her stockings if they are stretched, as seen in "The Diet Syndrome".
It's assumed that Stocking can transform her stockings into any other type of swords, but such is yet to be seen.
Even though Stocking said that she was a Demon at the end of the series, her swords still have the same blue/white colors, rather than Scanty's and Kneesocks' weapons, which are yellow/black colors.This could imply that Stocking is indeed an Angel.