The 401k represented another major innovation in yo-yo technology, as we've come to expect from the Van Dan Elzens. Hans and his team at YoYoFactory created the first yo-yo with an adjustable response system. Shuttles around the bearing move in or out, depending on how you adjust the knob on the outside of the yo-yo. So response can be increased or reduced, depending on how you advance or retract the shuttles.
While the 401k came with starburst response, stickers could be also used, making this a very flexible design. Look carefully at the shuttle around the bearing, and adjustment knob on the outside.
The Espionage featured a teflon coating, in black on this one, which gave a super slick finish. Yoyofactory was the first to ever try this coating on their earlier Grind series. It also featured the rubberized shuttle response system and their Dorothy bearing.
Pictured here is the white teflon version of the Espionage.
