PB bags are black polythene planter bags. The 'PB' stands for 'Pint Bag'. This means that PB1 will hold 1 pint of soil, or approximately 600ml.
To calculate the volume of soil held by the different sized PBs in metric terms multiply the number (e.g. PB2) by 0.6 to find out how much soil they can hold. Example - (PB)2 x 0.6 = 1200ml or 1.2 litres.
PB bags come in two pack sizes, 5 and 10 packs -
10 pack – PB0.75, PB1.5, PB2, PB3, PB5, PB6.5, PB8
5 pack – PB12, PB18, PB28, PB40