The way in which portfolio managers might be able to construct portfolios to benefit from anticipated changes in the slope of the yield curve is through the use of bullets or barbell portfolios. A bullet portfolio is one which has a portfolio of bonds whose durations are all pretty similar to the Target duration of the portfolio as a whole. Whereas a barbell portfolio is one which holds a number of lower duration but also a number of higher duration bonds than our Target duration, but such that those lower duration and higher duration bonds within our portfolio offset against each other to give us the same overall Target duration. So if we have a view as to where interest rates are going in terms of shifts in the yield curve, we can adjust the duration of our portfolio. But if we have a view as to the change in the slope of the yield curve, we can achieve the same Target duration whilst holding either a bullet portfolio a portfolio of bonds whose duration are all very close to our Target duration, or we can construct a barbell portfolio where we have a mini portfolio of bonds with a lower duration and another mini portfolio made up of a number of bonds or with a larger duration. Bullet portfolios outperform if we have a steepening of the yield curve. those bullet portfolios outperform a barbell portfolio if the yield curve steepens, so if we expect a steeper yield curve in the future, we could construct a bullet portfolio, which might outperform a benchmark If we anticipate that the yield curve is going to flatten a barbell portfolio will outperform a bullet to portfolio. So if we are anticipating a flattening of the yield curve, we can construct a barbell portfolio which will outperform a bullet portfolio and hopefully outperform our Benchmark as well. These two effects are independent of any shifts in the yield curve if the yield curve flattens but has either an upward shift a bear flattener or a downward shift a bull flattener that doesn't make any difference to this analysis barbell portfolios will outperform bullet portfolios no matter as to the absolute level of the year so long as we end up with a flatter yield curve the barbell portfolio will outperform.