So maybe a little clarity on the TelCom IDC (Insulation Displacing Connector) splicers:
They are typically for 19ga to 26ga and come in two styles-
"B" - white, indoor only, if you strip the wire they can do mixed stranded and solid. Not very reliable as a piercing connector, really need the parallel jaw tool to be reliable.
Button - red, blue or other, gel filled for indoor or out, they are meant for solid wire that is not stripped. They have a limited wire size range, so check the manufacturer's specs. The 2 styles are UR allows 3 wires to be connected together while the UY is designed for only 2 wires. Need to carefully press in the 'button', if you don't have the tool, I find adjustable pliers are better at squeezing it in straight vs plain pliers.