Anchor Boxed Sets of blocks are meant to be cummulitive. That is, sets 4 and 4a combined equal set 6. (Therefore, buying sets 4 and 4a is the same as buying set 6 except that set 6 is less expensive and comes in one box instead of 2) At this time, the duplication of 4 + 4a and 6 is the only duplication in the series. 4 and 4a are offered primarily for those who want to order a small set and see if this type of block suits their needs before investing in the more expensive sets. 4 + 4a = 6 ****** 6 + 6a = 8 8 + 8a = 10 ****** 10 + 10a = 12 12 + 12a = 14 ****** 14 + 14a = 16 16 + 16a = 18 ****** 18 + 18a = 20 ... all the blocks currently available. Sets 16a and 18a are due out in the fall of 2001. Instruction and design manuals in each box require all the cummulitive sets up to and including the highest number listed to build the structures pictured. What this means is, you can't start with set 14a unless you also order all the 6, 6a, 8a, 10a. amd 12a sets as well -- or you'll end up with a box of stones that don't build the blueprints included in the box. ********************************************* REACH US BY EMAIL AT purcifuls@yahoo.com OR BY PHONE AT (806) 239 2927 during business hours. IF YOU DON'T GET A LIVE PERSON -- JUST KEEP TRYING! THIS TIME OF YEAR WE TAKE LOTS OF CALLS!! ********************************************************* BE SURE TO CLICK THE GLOBE ICON AND GO TO OUR FRONT PAGE FOR CURRENT SPECIAL OFFERS AND COUPONS!!! ********************************************************* FOR COMPLETE SHIPPING DETAILS (what kinds are offered, how long it takes, how to choose etc....) CLICK THE "SHIPPING INFO" BUTTON on the left side of any page. ********************************************************* To find out about Purciful's Policies -- privacy, security, returns, placing orders by mail and phone, or just about us -- go to the ABOUT PURCIFUL'S AND POLICIES link -- it's in the column of purple buttons on the left side of every shopping page!