Specifications include, but are not limited to: This Invitation to Bid (ITB) is to solicit bids for Ultrablock interlocking concrete blocks or approved equals. This ITB includes a representative list of items to be purchased during the Contract period. The County may order other shapes and sizes as needed and any related accessories or products, such as sustainable blocks and items with customized strength or concrete specifications. Technical Specifications Product Name: Ultrablock Concrete Blocks or King County Approved Equal Standard size: 2.5’ x 2.5’ x 5’ Weight: 1960 kg (4320 lbs.) Clearance around key: 12mm (1/2”). The chambered corners provide approximately eight (8) square inches of drainage area per block. Minimum Radius of curvature: 23m (75”) for walls one block thick. Tighter curves and thicker walls may require special blocks. Surface Finish: Standard Grade: one (1) full face without large blemishes. Seconds: All faces may contain large surface blemishes such as honeycombs, chips, etc. Strength levels for concrete blocks manufactured with returned concrete “seconds” must be equal to the “standard” grade blocks. The average placing time for bottom rows should be approximately 10 blocks per hour and the average placing time for other rows should be approximately 20 blocks per hour.