I am currently working on moisture sensitive lyophilized drug product and subcutaneous preservative free solution. I have some question which are enlisted below:

1) What is the difference between 4405/50 Gray Bromobutyl rubbber stoppers and 4023/50 Gray Bromobutyl rubbber stoppers of west pharma?

2) What is the difference between 4423/50 Gray Bromobutyl rubbber stoppers and 4432/50 Gray Chorobutyl rubbber stoppers except chemical composition?

3) Which rubber stopper is best for moisture sensitive lyophilized drug product?

4) Which rubber stopper  is best for subcutaneous preservative free solution?

5) Which rubber stopper show less extractables and leachables profile?