Tricep extensions with kettlebells are great to isolate the tricep and build mass that will help you achieve a greater bench press.
Begin by lying on a flat bench with a kettlebell in each hand and resting on your chest. Next, extend the kettlebells over your chest and rotate your wrists into position; your palms should be facing your feet and the weight of the kettlebell should be on your side of your wrist. Next, bend at your elbows and lower the kettlebell down until it is even with your ears. Make sure to keep your elbows tight and do not allow them to flare out to the sides. Next, use your triceps to push the kettlebells back to the starting position. Repeat this movement until you have completed your set.
Your elbow should be the axis point, do not allow your upper arm to move at all while performing this exercise.
This exercise can also be performed one arm at a time, which may help some lifters focus on their form.