OKI Sheet Guide Assy (N), 1PA4094-7305G010, is a sheet-guide component listed for the printer’s upper-cover assembly. It is identified for the ML3390 and appears as the Sheet Guide in the ML5520 parts list.
The model distinction matters: the ML5521 parts list gives a different sheet-guide number, 1PA4094-7308G011. This description refers specifically to the N assembly with part number 1PA4094-7305G010. The cited parts listings do not specify dimensions or package contents.