This is actually called the "eccentric-accentuated compound-isolation incline kettlebell skull crusher." The name is a mouthful, but once you analyze each component you'll see why it's so effective.
It's a "compound-isolation" exercise in that the eccentric or negative involves an isolation movement in the form of a skull crusher, while the concentric (lifting part) involves a compound movement in the form of an incline press. This allows you to use supramaximal loads (greater than your 1RM) on the negative part of the movement and still be able to lift the weights back up.
This causes incredible stress and micro-trauma, an important mechanism of muscle growth. You'll be handling approximately 120% of your max load during the skull crusher, but roughly half that for the incline press.
Although this same compound-isolation protocol can be done in flat or decline positions, the incline allows the greatest relative workload (percentage of your 1RM) during the concentric pressing phase. The pressing phase becomes a semi-rest period that serves as a means of re-setting for the next heavy eccentric skull crusher.
The pressing phase also involves more activation of the lateral and medial head while the skull crusher mainly targets the long head. As a result, you'll trigger size and strength gains throughout the entire triceps region. Just be prepared to have incredibly sore tri's for several days.
To do it, lie on an incline bench set to 25-40 degrees. Using heavy kettlebells, perform a negative skull crusher by pivoting at the elbow and lowering the weight slowly to the sides of your head. Once you reach the bottom, pull the kettlebells toward your chest and do a standard incline chest press. Repeat for three sets of 5-6 reps.
To increase the intensity, once your triceps fail and you can no longer control the skull crusher phase of the movement, try doing an additional 5-6 strict incline presses. Your triceps will be pre-exhausted so they'll give out well before any other muscles, which makes this highly effective for stimulating size gains.