Blackburn CS77 AL SERVENTR COMP SPLICE A:1/0 B:1-2

The CS77 is a two-conductor service entrance compression splice with different sizes on each end: side A takes 1/0 and side B takes 1 or 2. That mismatched sizing is the point of the part, it joins a larger run conductor to a smaller service conductor in one crimp instead of forcing you to pad out the smaller wire.

Yes. The CS77 complies with ANSI C119.4 when properly installed on aluminum-to-aluminum or aluminum-to-copper conductors, so it is rated for both all-aluminum runs and AL-to-CU transitions. It is also RUS accepted, which matters on utility and rural electrification work.

Compression only. The CS77 is a crimp-type splice with no set screws, so it takes a hydraulic or battery compression tool with the correct die for the barrel. If you want a wrench-installed joint instead, look at a mechanical set screw splice rather than this part.

It is a bare connector, no insulation is supplied with it. Plan on insulating the finished splice yourself with tape, heat shrink, or a cover appropriate to the voltage and location, or house it inside enclosed gear.

A crimped joint like this one is permanent and tamper resistant, which is what utilities and inspectors usually want on service entrance conductors, and it holds its contact pressure without retorquing. A mechanical connector is the better pick when you need to reopen the joint later or you do not have a compression tool and die on the truck. The tradeoff is that once the CS77 is crimped, the splice is not coming apart.

Each. One CS77 splice per unit, so order one per joint plus spares for miscrimps.

Blackburn part number CS77, made in Mexico. That MPN is what to quote when matching an existing splice on a service or specifying to a utility standard, since the sizing combination (1/0 to 1-2) is what distinguishes it from the adjacent CS numbers in the family.