I am looking at doing a bulk purchase of fittings for my new project. As I am a first time WC'er I need some advice on BP fittings before I make my purchase. Can someone explain the difference between these two products. There is an obvious physical difference, though I am not sure what the difference in functionality is. http://www.gammods.com.au/store/index.php?main_page=product_info&products_id=1569 http://www.gammods.com.au/store/index.php?main_page=product_info&products_id=1570 Also, do 7/16"-5/8" BP Compressions screw nicely into EK Multioption Res's? I think I remember reading that large compression fittings do not seal real well against the end caps of the Multioptions and extensions are sometimes needed to ensure a water tight seal.