Not only can you leave your plants safe in the knowledge they'll be automatically watered correctly, you can also add liquid plant food to boost growth and yields. Easy to use, they come in a pack of 8 with full instructions. The cap measures 28mm across, so fits all bottles with a 25mm neck size.
Some examples of bottles that the irrigation kit fits:
All Schweppes and Coca-Cola bottles
Fanta bottles, Dr Pepper bottles, Pepsi bottles, 7-Up bottles
Tesco own brand bottles 1 litre plus
Waitrose own brand bottles 1 litre plus
Sainsburys own brand bottles 1 litre plus
Asda own brand bottles 1 litre plus
M&S own brand bottles 1 litre plus
Morrisons own brand bottles 1 litre plus
Plastic Wine Bottles
Highland Spring 1.5 litres
Fairy Liquid bottles
Ecover bottles
Please note: smaller, 50cl bottles tend to have wider necks that don't fit, while the larger bottles have smaller necks that do fit. Does NOT fit Volvic and Evian bottles.