The wide-bore (also called mega-bore) column is a capillary column with an internal diameter of 0.53 mm and a film thickness normally of 1.0 - 5.0 μm. Of all capillary columns it is the least efficient and the 'slowest' column in performance.

On the other hand, its capacity is by far the largest. That is why the wide-bore column is so unique compared to other capillary columns and to packed columns.

In spite of the fact that the capillary fused silica column offers many advantages, packed columns are still used today.

Four reasons for using packed columns:

1. Equipment not suitable for capillary columns: Due to the small sample capacity of a capillary column, GC systems normally used for packed columns must be modified or a new apparatus has to be purchased. Modification of existing instruments can often simply be carried out using modification kits.
2. With older generation of instruments, repeatablilty of injections might not be good enough for capillary columns: When using the most widely employed injector in capillary GC, the split injector, only a small portion of the injected amount of sample is introduced into the column. This small portion is not always sufficiently reproducible, causing the injected amount to be never exactly known. This is especially valid when discrimination occurs. The ratio between the split amount and the amount introduced onto the column is not the same for all components.This arbitrary distribution of the components between the split and the column will result in inaccurate quantitative results if no (good) internal standard is used. The direct injector used with packed columns does not have these problems. For that reason packed columns are sometimes preferred.
3. Some applications need large sample capacity columns. In that case packed columns are preferred to 'normal' capillary columns. The ideal case would be to have a column that could be operated under packed-column conditions, with a sample capacity comparable to that of a packed column, but with the advantage of a capillary column, such as adequate separations and fast analysis times. A column that approaches this ideal is the wide-bore fused silica column, which can be regarded as an intermediary.
4. Some standard methods still require the use of packed columns.