5 & 1/4

Being a five and a quarter is when someone is being "floppy", by flip-flopping on an agreement when they said they would do something (or act a certain way), then change their minds. 5 1/4 is taken from the old 80's era large 5 1/4" floppy disks, the floppy disks that were actually floppy.

Don't be a 5 & 1/4, you said you would help fix my computer, don't be a dick.