It can be done without silicone...
This vacuum breast pump allows you to exercise and enlarge your breast with vacuum pumping.
The breast pump has two transparent suction cups, which are attached to a practical scissor handle pump.
Place the suction cups over your breasts and make sure that the edges are tight. Then use the pump to create a vacuum in the suction cups. This will increase the blood flow to your breasts and they will swell and become more sensitive.
With the air pressure valve you can easily regulate the vacuum in each suction cup separately.
After use, clean the suction cups for hygienic use with a Toy Cleaner or mild soap.
Inner diameter of the suction cups: Size M = 10,4 cm