Knitted knockers

I’ve been told that these are made of cotton by lovely ladies free to mastectomy ladies. I sent for one. I have a softie provided by my breast care nurse but I am sure it will be very hot in the summer. Flat friends ladies tell me that they move around a bit and need weighting with pound coins! I wonder how my bra will cope with one normal, droopy boob and one lightweight one. I bought a post surgery bra from Asda. It felt very hot when I tried it on.