for the 2nd age and the use of thickened milk, with its 3 speeds: low, medium and high.
Advice: even if the teats were well cleaned with soapy water, steam sterilization of water in an electric sterilizer is recommended to eliminate all bacteria.
Tricks: to keep elasticity teats, sterilize them with steam in an electric sterilizer. Soaking in boiling water or maceration in some chemical product accelerates their aging and gives them an unpleasant taste.