I have been advised that McMaster Carr distributor is not carrying true Multicore (TM) solder, but an imitator called "Multiwire" or similar. Please go to the Loctite Corp. web sites or google search "Multicore Solders Inc." to find true Multicore distributors. They should be same places that carry the Loctite brands of thread locking products and chemicals. 72, Stuart K5KVH