North Circuit Breaker Lockouts
Single pole circuit breaker lockout Requires a switch breaker with a recessed hole in it. 
Accommodates breakers up to 9/16" (14 mm) wide.
Double pole circuit breaker lockout Requires the breakers to be connected with a cross bar for lockout applications. Accommodates breakers with an overall Width" of 1 7/8" (48 mm).
Single pole circuit breakers lockout
Does not require a switch breaker with a recessed hole in it. 
Accommodates circuitbreakers with an overall Width" of 1/2" (13 mm).