Omnipure Q5667 Water Filters are designed to fit. Omnipure Twist Tap filter heads QNVH B, C, or J, with or without automatic shutoff. If you do not have a head for the Omnipure Q-Series filters, you can purchase one of the Omnipure Q-Series heads below in the Related Products section. These heads are valved. which means the water will automatically shut off when replacing the Q-Series water filter. The heads are available with 1/4" Quick connect fittings, 1/4" NPT, or 3/8" NPT. Omnipure Q5667 GAC KDF Water Filter Specs:. Dimensions: 2.5" W x 12" L. Fitting Size: This Q-Series filter is a replacement filter and must be used with an existing Q-Series head. The Q-Series heads are available in 1/4" Quick-Connect fittings, 1/4" NPT female threads, or 3/8" NPT female threads.