There are four options for the choice of head material for your laboratory pumps. It is important that you choose the correct option for your application. Typically the most important factor is the chemical compatibility. PEEK (polyetheretherketone) is an engineering plastic. It is hard and will be suitable for applications up to around 6000psi. It is recommended for liquids that may contain salts or acids that may corrode stainless steel. It is not recommended for organic solvents. PEEK laboratory pumps must be used with PEEK fittings. Stainless steel fittings must not be used as these can damage the threads of the pumps. Stainless Steel. There are various grades of stainless steel and its important to use the correct grade. All our heads are made from 316 which is highly chemically resistant, particularly with organic solvents. It may be corroded with buffer salts. Stainless steel is physically very strong and we use it on all out ultra high pressure laboratory pumps. They pump can be used with either stainless steel or PEEK fingertight fittings. Most applications will be fine with Stainless Steel or PEEK, but if you are working with particularly harsh reagents then Hastelloy and Titanium are also available (these are more expensive). If you require these then please contact us. The SFC pump is fitted with Aluminium heads. These are designed for pumping liquid CO2 and Aluminium is used as its heat conducting properties are better than Stainless steel.