Several companies offer transfection reagents. Our collaborators have used TransIT®-mRNA Transfection Kit (Mirus),  Stemfect™ (Stemgent), mRNA-In™ (MTI-GlobalStem), RmesFect™ Transfection Reagent (Oz Biosciences), and Lipofectamine™ RNAi Max (Life Technologies) with success. We suggest testing a matrix of transfection reagents and varying ratios of RNA to transfection reagent. Just as with plasmids and oligonucleotides, the optimal transfection procedure will need to be determined empirically. Some cell types are intrinsically easy to transfect (e.g. HEK-293 cells ~97%). Efficient delivery to other cell types, such as some primary cells can be very challenging.