We are often speaking and talking about, and lot of us have difficulties to make a choice between the different sizes of double balloon nozzles .
I made this size "experience" if you doing it your self , be sure of the tightening of the hose on the bulb .
Take a bulb Nr.8 the volume equals 250cc ,
I remember you that german d b nozzles are made with two balloon inner and outer of 250cc
silicone d b are from two types 500cc (inner) 250 (outer) and 750cc(inner) 250cc outer .
Now take your bulb nr 8 and tighten the hose on the nozzle of the bulb,
squeeze the bulb to make it empty from any air , suck at the outer side of the hose ,
now that the bulb is empty lube it land your anus too ,
fold the bulb and shove it in your anus , then inflate it , you will feel what is the volume of 250cc when the bulb will be inflated , and you will understand that 250cc is large enough to fill your rectum completely .
To evacuate the bulb suck at the end of the hose and pusch the bulb out of your rectum leading it with a light traction on the hose .