PEG-b-PLL is a di-block copolymer of poly(L-lysine) PLL with mPEG (linear PEG terminated with a methoxy group). PEG-b-PLL is positively charged at physiological buffer pH and can be used for delivery of DNA and RNA. It is an effective transfection reagent and also a good choice for drug delivery. MW of 6k, 12k and 24k of the PLL corresponds to roughly 50, 100 and 200 lysine repeating units. The indicated MW does not include the counter ions. Counter ions for the lysine units are chloride (Cl from HCl hydrochloric acid). We provide custom synthesis for PEG-b-PLL with a variety of MW options; PEG MW could range from 1,000 Da to 30,000. The product is typically supplies as the HCl salt but can be made with other counter ions (TFA salt or HBr salt) or no counter ion.