3M UR2 Scotchlok Connector

The UR2, solvent resistant connectors, accept two or three solid copper conductors that can be of different wire gauges, for butt splicing. 
Scotchlok UY tap connector

Uses the principle of self-stripping connection by the U-shaped metallic element
The UR2 connectors are filled with a sealant to provide moisture resistance.
Grease filled connector for 2 or 3 wires
Max out diameter: 2.08mm
Cable diameter: 0.4 - 0.9mm
Cap colour:  Red
Applications: telecommunications (all networks including ISDN and Numeris), low currents, alarm systems etc
The E9BM crimping tool is recommended for crimping UR2 connectors on conductors with a diameter of 0.8 or 0.9 mm
Manufactured by industry leaders 3M