Theses are in-house amalgams of their own proprietary funds with low expense ratios whose portfolios shift asset allocations according to the time horizon remaining till your retirement date.  The longest time horizon (target date of 2035 for example) has the lowest allocation to bonds while the shorter target dates hold more bonds.  An excellent retirement savings vehicle for 401-ks and IRAs my preference tilts toward Price but they are all decent IMO.

Peace and love,

Flakey