I guess he mean Laimington RD....i guess
I suggest instead sell of ur existing ram and go for two sticks of same speed and company...will serve u better and give u better speed.......
knwing just speeds ( 533Mhz/ 667Mhz ) is not enough if u plan to buy just one stick for ur existing RAM....u should laso know latency timmings...which are usually 3-3-3 or 2.5-3-3 etc usually written on ram...note that also while buying a identical ram......