Loctite 243 10ML Threadlocker - medium strength LOCTITE® 243 is a general purpose blue threadlocker of medium bond strength. This threadlocker secures and seal bolts, nuts and studs to prevent loosening due to vibration. The product works on all metals, including passive substrates such as stainless steel, aluminium and plated surfaces. It is proven to be tolerant of minor contamination due to industrial oils, e.g. engine oils, corrosion prevention oils and cutting fluids.