Which printers does this assembly fit?

It is made for the Canon MF series models Canon lists against part number MF1-4615-020. Check your printer's model and part number before ordering, since other MF machines use different platen assemblies.

Is this the glass only or the whole frame?

It is the upper reading glass assembly, meaning the platen glass with its surrounding frame as a unit. That is what you replace when the glass is cracked, scratched or fogged.

Can I install it myself?

It is a service part that requires opening the scanner section and removing the old assembly. Someone comfortable with printer repair can do it; otherwise a technician should.

Will it fix streaks or lines in my scans?

If the marks come from scratches, cracks or clouding on the platen glass, replacing the assembly addresses them. Streaks caused by the scan head, rollers or software will not be fixed by glass alone.

Is a genuine Canon part worth it over a third-party copy?

A genuine assembly matches the original fit and glass quality, which matters for scan clarity and lid alignment. Third-party copies can vary in flatness and frame fit.