For heat shrink crimp connectors I buy the good ones from Wurth or reputable automotive parts supplier. I bought a bunch from Amazon and the metal portion must be Chinesium - very soft and I didn’t like the resulting connection. I don’t use a ton of these so I don’t mind paying a little extra. When I really care about the connection, I solder then apply heat shrink tubing with adhesive. I found the Harbour Freight marine grade heat shrink tubing to be of decent quality. Heavy wall with a good amount of adhesive.