These little tabs are a staple in my backcountry kit. They're so convenient and they don't impart a strong nasty flavour like the old purification tabs of yesteryear. Just dissolve in your 1L water bottle, wait 30 min and drink.
The package contains 50 tablets, yet the whole box is small enough to fit in your shirt pocket. Whether these are your primary purification source, or secondary, I highly recommend taking them with you on your next trip (I usually have a few stashed in different places such as with my toothbrush to queue filling my water bottle at night). Active ingredient (per tablet) is 8.5 mg US EPA approved Sodium Dichloroisocyanurate (NaDCC) equivalent to 5mg/L free available chlorine. Bilingual package. This item is available for pick-up. Please enquire about shipping rates.