 One part of FSL solution is added to one part of cells (up to 100% suspension) and they are incubated at a set temperature within the range of 4–37 °C (39–99 °F) depending on temperature compatibility of the cells being modified.The higher the temperature, the faster the rate of FSL insertion into the membrane.For red blood cells incubation for 2 hours at 37 °C achieves >95% FSL insertion with at least 50% insertion being achieved within 20 minutes.