BLOCK-iT Pol II miR RNAi expression vector kits combine artificial miRNAs and the tissue-specific options of pol II promoters with the traditional advantages of RNAi vectors. In addition to stable and/or regulated expression and viral delivery options, over 70% design success means users can screen fewer clones. Moreover, users can track miRNAs with co-cistronic GFP expression and easily knockdown various pathway components using multiple target knockdown sequences per transcript. Invitrogen Corp. 800-955-6288 www.invitrogen.com