Wrench, 1/4" x 5/16", Open Ended. Flat. ARE-Applied Research brand. 5/PK.
Additional Info:
This wrench is chosen for use for HPLC Instruments and Columns due to the size of the flat but also due to the optimal length of the shaft. This length provides sufficient leverage needed for tight fitting without requiring too much force by the user.
The opening covers the nuts without excessive over-hang.