For your electrical toolbox.

No thanks, I had it beaten into me by my instructors as an apprentice that you make a good mechanical joint BEFORE you apply solder. Ain't seen or heard nuffin in the nigh on 40 years since to convince me otherwise!

If they were crimp and heat shrink connectors I might go for them though
 
Weird.....I have never come across these before. I agree with Erbas, but I guess they must have some specialised desirable use somewhere? Heating them up enough for the solder to melt also sounds fun in a confined space. Oh!...and there's the price at over 55p a go.
 
I've used a few - good for quickly making medium-term repairs in damp places before I bit the bullet and rewired the whole boat. Not sure why the OP has had difficulty finding them though.

The solder seems to be some kind of special low-melting-point alloy, as there's no need to apply an iron to it. You simply push the two stripped wires in so that their strands interweave, then apply heat. It's much easier with an electric heat gun, though a gas flame will do in a pinch as long as you're careful not to scorch the plastic. The solder melts and forms what appears to be a good bright joint between the wires, then the plastic shrinks and the adhesive melts to glue it all together, providing strain relief and waterproofing.

Quick, easy, I can't see too much wrong with them except for the price.

Pete
 
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