does anybody know the differnce in these arp head studs

[combs-dsm]

I found 2 different styles of arp head studs. There are 2900 series and 3800 series for my 96 eagle talin tsi awd. Im geussing theres a difference in pressure holding but not sure. Can anybody shine in on this.

 

[99gst_racer]

I've never heard of them listed in various series'. Do you have part numbers for both?

 

[combs-dsm]

Sorry this was a 3900 not 3800
ARP 207-3900 Head Stud/Bolt Kits - eBay Mobile (item 140909287720 4/23/2013 7:10:06 PM)

And this one is the other 1 i saw
http://wap.ebay.com/Pages/ViewItemDesc.aspx?emvAD=320x480&aid=140909201372&emvcc=0&nbcol=0|null

 

[99gst_racer]

207-4203 is 7-bolt head studs.

207-3900 is 7-bolt head bolts.

 

[combs-dsm]

Thanks for clearing that up for me