The product itself
The refills are 300 ml.
In terms of how long until you need to refill, this will be individual depending on how often you use the product(s), how many people are using it, and whether you are in a hard or soft water area. Generally though, a refill should comfortably span 4-6 weeks with average use.
The refill bottle
Unlike conventional plastic bottles that persist in the environment for years, our Vivomer refill biodegrades in biological matter (it's made from microbial fat so just breaks down into this!) What's EXTRA cool about this material is that it ONLY breaks down in soil environments as it needs those bacteria to break down. This means that on your shelf or in your bathroom the refills are as shelf-stable as conventional plastic.
Check out this time lapse photo series of the refill once in compost conditions over 0 months, 1 month, 2 months, and 3 months.
We even took it out of the compost environment at about 1.5 months and put it in a dishwasher cycle. It came out in exactly the same state (if a little less muddy) because the breakdown stopped once it was removed from the soil.
Neat, right?