Pro

For example:
"90-92 IROC-Z Z28 TA GTA TPI TUNED PORT INJECTION LOWER INTAKE 10088016 USED # 3"
And
"89-92 IROC-Z Z28 TA GTA TPI TUNED PORT INJECTION UPPER INTAKE PLENUM USED # 1"

I am just gathering up parts and dont need a mixup.

GeneralDisorder

iTrader: (1)

It's just how the seller is organizing the parts so he knows which one you wanted. The number corresponds to some markings he has made on the parts so he doesn't mix up which ones you ordered based on the pictures in the auction listing.

GD

jmd

iTrader: (4)

Like Gen Dis said, tracking.

And other times, they do it so the item erroneously shows up in more search results.

Pro

Cool. I thought it might have been some stupid part number matching thing GM did. As if they put out 8 different types of runners and you had to get the match up the correct upper and lower. Thanks

jharrison5

When I was selling a bunch on ebay I did it to stay organized just like JMD and General said. When you have 10-15 listings going all with close end times and you're selling like items it can get a little bit tough to keep it all in order.