This kit updates your Switchblade 250 Tricopter to a Trident 250. The Trident uses the same hardware as the Switchblade but replaces the front folding carbon tube arms with fixed printed arms. This reduces the overall parts count and cost of the design. To build this tricopter you will need to also download parts and follow the instructions found in the Switchblade 250 "thing" http://www.thingiverse.com/thing:755420 This kit includes a left and right arm, and printable bushings which replace the ball bearings in the Switchblade frame. Four (4) additional M3 self tapping screws will be needed, but you can use the same length ones used to secure the tail boom in the Switchblade. Keep an eye out for a full Trident 250 Tricopter "thing" which will include all files needed to built a Trident 250 Tricopter along with simplified arm mounting and reduced printed part count.Please see Switchblade 250 page for instructions and parts list. http://www.thingiverse.com/thing:755420/#instructions