Still based on tek's mk1 design and developing the mk2 derivitives of Jeffery Sanders. Featuring a new quick release hot end system and adjustable x-axis end stop screw. This extruder is even simpler to assemble and requires even less nuts and bolts.Video demonstration of hot end change: http://youtu.be/1w0qsRLDrN4Print all parts at 50% fill or greater for strength.Tensioner arm may require extra perimeters to eliminate gaps.Users not wishing to use the quick release system can use the older mk3 retainer as it is more stable.Instructions can be found here:http://www.soliforum.com/topic/1265/jigsaw-replacement-mk4/Dimensions in mm.