whats the diff between head studs & main studs?

[civicious]

http://www.prostreetonline.com/buy/arp_main_studs/
http://www.prostreetonline.com/buy/arp_head_studs/

whats the difference?

 

[Loco Honkey]

Head studs hold the head to the block, and main studs hold the main bearing caps to the block.

 

[hcivic.com]

ya you beat me to it