Slide the tubing over the cable before you connect the wires to the splice block. Then slide the tubing over the connector and shrink it with a heat gun (best) or a torch (gently). The other type ...

Every listed wire connector has a minimum and maximum size ... Gather the stripped conductors that you will be splicing into ...

which is made up of rows of four IDCs that are used to splice pairs together. There are also 110 blocks that connect a punched down wire on one side to preconnected patch cords with connectors ...