For use with the spool coaster sold on printrbot.com. With this, the spool can be placed on top of the 12mm smooth z-axis rods. The Adjustable Spool Coaster can be purchased here:http://printrbot.com/shop/spool-coaster/The Old-Style Coaster can be purchased here:http://printrbot.com/shop/spool-coaster-old-style/Designed By: Tommy BertkenThe Printrbot Printrn