Squirt Sealant is a long life span sealant at a decent price. It contains a mix of latex and microfibres to which you add "beadblock" particles to so that you're covered for a wide range of hole sizes (apparently up to 6mm). Unlike some other sealants, it doesn't clump in the bottle even after being open for months.

Like all sealants, make sure you shake it properly before use, otherwise the particulates might remain in the bottle (they settle after a while).

We have two sizes of this product:
1L: for doing a bunch of tyres over time. 
120mL (pouch): A single tyre serve. Store it in your car for the inevitable day that you need it with urgency 😊