In the UK there are only two types currently available: Silicon gel and saline.
Silicon has been in use since the 1960s and the majority (about 80%) of UK implants use this. One type, PIP, was commonly used until a health scare in 2010, after which many women had their implants removed (in some cases industrial-grade silicon was being used to save money.) There was also a polyurethane coated implant in the past, but this was withdrawn in the 1990s.

Saline implants also involve the use of silicon: A sort of shell is made from this substance and filled with a saline (salt-based) solution. This option is less popular, but considered safe.

Other types of implant are available but not allowed in the UK, mainly for health reasons. Types which can be used in some countries include titanium coated implants, soya bean filled and hydrogel filled.

You can find out more about the different types of implant here.