Our Highest Purity Softener Salt Pro's Pick Dura-Cube Our premium-purity water softener salt contains up to 99.8% pure salt. Virtually 100% water soluble, it is uniquely compacted for hardness to prevent mushing and bridging in the brine tank. This helps to keep your softener clean and trouble-free. DURA CUBE Lehman FEED MILL 50% Family Owned & Operated Since 1954 DURA- CUBE 5111 S. 000 Rd. Berne, Indiana 260.589.2451 DRIVE THRU Inc.