KnitPro Afghan / Tunisian Crochet Hook Connector
These are great and super versatile!
This is what you can do with them:
Connect two interchangeable crochet hooks end to end - You can then Afghan crochet or Knook.
Add one to the end of a interchangeable crochet hook, along with a cable end stopper. You can also add a cable connector, or combinations of connectors, to make the crochet hook longer, so you can do Tunisian crochet of various widths.
You can add one to the end of interchangeable needle tips, along with a cable end stopper, to turn you needle tips into single pointed needles. And you can add a combination of the connectors to make them longer.
You can add an interchangeable crochet hook and needle tip together - some kinds of crochet are worked like this.
You can add them between interchangeable needle tips, to make DPNs.
The Knit Pro interchangeable range is compatible with Knitters Pride (same company but in the US under a different name). And also with Knit Picks, Drops, and Knit Pro for Prym - they all all the same product, just rebranded, and also available in different wood colourways depending on the company.
Now about the product itself -
A cable key is included in order to tighten them, so they don't come loose. I have never had any needle tips or cables or connectors come loose at all. Just be sure to hold at the metal base of the hook or needle tip (to prevent any breakages). Also, the joins are smooth and seemless, and don't catch or snag on the yarn.