Interval Space Required：1 3/8 Inch Spacing between main and generator breaker.Refer to Figure 4 for installation. There is a slight error in the instructions.The subsequent instructions have been changed, thank you for your feedback.SD-200A：Generator interlock kits are available for Square D QO and Homeline 150 and 200 amp panels.Safe use：the manual transfer switch device allow portable generator safe back feeding power supply to distribution panel and home line. Prevent utility and generator supplies from being ON at the same time. Aren't putting electrician in dangerous and damage electric devices during power outages.Package：Our Generator Interlock kit include 1 × Interlock plate, 3 × Screws kit, 1 × Drill Bit, 1 × Instruction Bulletin, 2 × Generator Start-Up Procedure Label, 8 × Remind Label, 2 × Zip Ties.Buy No Worries：All of our interlocking kits come with a lifetime warranty.Simply email us back if our product ever fails you and we'll mail you a new original replacement free of charge. Product Description Generator Interlock Kit for Square D QO or Homeline Indoor or Outdoor with Main 150 or 200 Amp Panels With the aging electrical infrastructure and frequent severe weather,The power outage resulted in affecting thousands of homes across the country. Aippwi's Interlock kit provides a safe and easy solution when using backup power. Our interlock kit prevents utility and generator supplies from being ON at the same time.Protect the appliances being used from being burned out due to power failure. Aippwi Generator Interlock Kit A reliable and economical way to meet your power needs. The Aippwi generator interlock kit allow safe backfeeding of a home through a portable generator during power outages. It eliminates unsafe generator backfeeding situations that could potentially electrocute electric power company workers or destroy the generator. Our devices will allow only one main circuit breaker to be in the ON (I) position at any time. The bracket slides between the handle of the utility main circuit breaker and the handle of the generator supply main circuit breaker.The screws do not need to be torqued tightly, resulting in the inability to move the interlocking kit Detailed installation introduction, packed with installation instructions. Keep Your House Safe And Ready For a Power Outage! Detailed installation introduction, packed with installation instructions. Interval Space Required 1 3/8 inch 7/8 to 1 1/4 inches 1 1/4 to 1 1/2 inch 3 1/4 to 4 inch Interval Space Required 1/4 inch 1 1/4 inch 1 1/4 inch 1 1/2 inch 2 1/4 inch