Strange Difference in transfer rates on identical cruzer flash drives. Why no replies?

I have several Cruzer flash drives, 2gb, 4gb, 8gb & 16gb.

While a few of the 2s & 4s are a couple of years older, the 8s & 16s were purchased fairly recently.

I’m getting wildly different transfer rates copying files TO the 16gb drives.

Both are SDCZ36-016G formatted FAT32, not NTFS.

One transfers from 8-10MB/sec & the other chugs along at 1-3MB/sec

I get similar discrepancies between the 8gb drives and a couple of the 4gbs.  Some are really fast & others, with the same model # are dramatically slower.

I’m using Windows 7, 64bit, USB2 on the system, not thru a hub.

This really makes no sense to me. 

I’ve tried reformatting the drives both on my Win7 machine and on my XP laptop, but it makes no difference.

All other settings are identical.  The only difference is the transfer rates.

Does anyone have any suggestions?

The only thought I’ve had is that while the drives appear identical on the outside, the insides may, in fact, be different.  Is there any software or utility which can determine what chips/hardware are actually inside??

Does anyone have any input on this issue?