Both kits use ProtoScript II Reverse Transcriptase for First Strand cDNA Synthesis. ProtoScript II Reverse Transcriptase is a mutant M-MuLV Reverse Transcriptase with reduced RNase H activity and increased thermostability. NEB #E6560 is a kit for first strand cDNA synthesis; its product can be used for downstream PCR or qPCR analysis. NEB #E5315 is a One-Step RT-PCR kit; its product is a specific dsDNA PCR product.