K’NEX 521-Piece Value Tub for $15.00. Shipping is free on orders over $25. If needed, use this Filler Tool to pad the order to qualify for free shipping. Here is a screenshot for your reference. It is compatible with all LEGO building sets and comes with ideas and instructions for 35 suggested models. Alternatively, it is also available at Walmart for $15.00 with in-store pickup. Most places have it for about $24.