Check the listing for details. SIEMENS ELECTRICENTER ECQL1 BX231M QL1 BREAKER LOCK HANDLE BLOCKING DEVICE. Condition: New. Listed at 2.50 USD. THESE ARE SIEMENS ECQL1 (SINGLE PIECE) CIRCUIT BREAKER LOCKS TO KEEP IMPORTANT CIRCUITS ( LIKE ALARM, OR SUMP PUMP) CIRCUITS FROM INADVERTENTLY BEING TURNED OFF. THEY WILL NOT STOP THE BREAKER FROM TRIPPING JUST MAKE SOMEONE THINK TWICE ( AND BRING A SMALL SCREWDRIVER BEFORE TURNING OFF A PROTECTED BREAKER ) THEY ARE GREAT FOR PROTECTING ALARM CIRCUITS OR SUMP PUMP CIRCUITS OR ANY OTHER BREAKER YOU DON'T WANT ACCIDENTALLY TURNED OFF. THEY FIT MOST ITE/ SIEMENS AND MURRAY BREAKERS, BRYANT, GE, SQUARE D QO, CUTLER HAMMER, T & B, CHALLENGER & HOME LINE BREAKERS. ABOUT THE ONLY BRAND OF STANDARD BREAKER THEY DON'T FIT IS THE TAN HANDLE CUTLER HAMMERS & FEDERAL PACIFIC STAB LOC'S. IF YOU WANT TO KNOW IF THEY FIT A PARTICULAR BREAKER MESSAGE ME AND I WILL TRY AND CHECK IT OUT.