"Flexible silicone" refers to a type of material that is soft, pliable, and bendable. It is made from a substance called silicone which allows it to be easily stretched or twisted without breaking. Full definition
These breast shells are made with a soft, flexible silicone back to mold to your body. (expressing-mama.com)
The non-stick flexible silicone and the wider, round cubes enables you to release portions individually or as many as you need without disturbing the other cubes. (amazon.co.uk)
A nipple shield is a thin flexible silicone cover which a mother places over her nipple prior to breastfeeding. (breastfeeding.asn.au)