This is the bottom portion of the T-2 traveler car assembly (HC 105). It was used on pre-1994 Hobie 14, 16 and 17 cats. If the upper half of your car is OK, you may be able to replace just the lower roller.
This car is no made to be "universal" which means, on some applications such as fitting it to the older Hobie traveler car tracks, the new traveler car base will need to be filed/sanded down approx. 10 thousandths of an inch to enable it to fit the tracks.