I am getting ready to Order my bong and stuff and i just wanna make sure this will all work when i get it. Messias Illusion Double 5-arm Percolator Bong - English - Grasscity.com 29.2 to 18.8 HQ 4 Arm Diffuser Downstem - English - Grasscity.com The 13.5cm one or should i do the 13cm one? Magic Glass - Twenty Niner Precooler 29.2 mm - English - Grasscity.com what does it mean by 29.2 > 18.8? does that mean one end is a different size than the other? Also, does this precooler need a bowl? it looks like it comes with one the precooler acts as a ashcatcher also correct?