there are two versions of this drive, one is 1620 and other one 1620 Pro. Also so many F/W released for this drive.
The only difference is the 1620 PRO is RETAIL drive and the regular 1620 is a OEM version of the drive. there is no hardware difference with both drives. if you get the OEM version of the drive you can use the official BENQ FIRMWARE so the drive becomes 4x DUAL LAYER DVD+R. Usually the OEM drives come with "G" firmware. the RETAIL drives usually come with the "B" firmware. You can crossflash the drive from a "G" firmware to "B" firmware. Here's the link to crossflash the drive:
you need to download the WinDWFLASH.exe file and the B7P9 cvt. file. you could also use the other firmwares like B7S9. B7P9 is what I use with no problems. you can flash the drive in windows or in safe mode. make sure you have no disc in the BENQ, turn off all the programs running in the background such as antivirus software. then double click on the WinDXFLASH.exe file, direct it to the cvt. file and let it flash the drive. it will tell you when the flash is done. reboot the pc and your drive is crossflashed to "B" firmware. some people reboot the pc twice. the "G" & "B" firmwares are supposedly the same. just OEM is "G" firmware and "B" is RETAIL. hope you understand and check out the BENQ FORUM at CDFREAKS.COM.