If you choose not to purchase the adapter, you can easily transfer your milk from your collection container because each bag has a wide opening. (themamaneeds.com)
After speaking with a lactation consultant and doing a weigh - feed - weigh we discovered that she was not effectively transferring my milk. (happeningsoftheharperhousehold.net)
In general, you'll have to express or pump into a different container and then transfer the milk into the bag for storage. (verywellfamily.com)