This is our original Big Blu microleak detector downsized into a Brush On applicator. This product is great for spot leak applications and is supplied with a 10 inch extension dauber. Big Blu is a well-established bubble leak detector solution capable of detecting micro gas leakage down to 0.65 oz/yr. It is a strong persistent film forming liquid that has excelled in the field identification of gas leaks. Big Blu is used by OEM's and industry professionals worldwide. Suitable for use with all gases to detect leaks on any pressurized system. Commonly used in HVAC, plumbing, telecom, aerospace, gas utilities, service industries and MVAC.