1 1/8" BARBED IN-LINE CHECK VALVE1 1 8 Barbed In Line Check Valve(W755): All FatSac fittings are machined in house and proprietary to our brand. This allows us to work creatively with OEM and custom sac customers to dial in exactly what you need. It also gives us control over the quality of fittings being used with our sacs. After all, the sac is only good if the fittings are airtight! The W755 check valve should be used in all after market automated ballast systems. A check valve is