A convenient to powerful and Value for Money of the 1. Hydrolytischen Class Glass Bottle Closure Combination for Unkritische analysis. A Smile Star diaphragm allows easy penetration of PE (polyethylene) mechanism. Recommended for use in the HPLC. For the 1 ml Flat Base glasses are plugs with or without a slot lock for Micro inserts available for a nominal fee. Plug without a slot lock show a better valve effect in creating a vacuum is not.