HP C9121A Q7709A 128MB 100 pin SDRAM MEMORY DIMM for HP LaserJet 4200 4200n 4200tn 4200dtn 4200dtns 4200dtnsl One 128MB PC100 100-pin sodimm Part#: C9121A, Q9121A, Q7709A 100% compatible with lifetime replacement warranty Manufactured by Keystron, LLC Keystron is a registered trademark of Keystron, LLC