Dryer vent hoses come in many different sizes and lengths. For the most part, each hose has about the same diameter. Some hoses, however, may not fit the particular vent you are trying to cover. This happens most often when fitting an older hose over a newer dryer, or vice versa. If this problem occurs, there are ways to make almost any dryer hose fit over any dryer vent. This will save the expense and bother of purchasing a whole new vent, hose or even dryer.
If you have a flexible hose, clamp the hose around the metal vent protruding from the hose. Dryer vent clamps are sold at any home supply store. Non-flexible metal hoses that are too large for the vent can be held in place with silicone caulk. Apply the caulk to the gap between the two items, and hold in place with a clamp. If the hose is significantly larger (which is uncommon), you will have to replace the hose.
If the dryer hose is too small, try to make the hose larger, or replace the dryer vent with a smaller vent. Both of these options may be difficult, especially if the dryer vent is built into the rest of the dryer. Dryer hoses are typically not built for expansion. A flexible hose is easier to manipulate than a stiff hose. With gentle but firm pressure, pull the hose open with your hands. This option may not work, or may damage the hose. If this option does not work, you will have to find a larger hose. Make sure to measure the vent size before purchasing another hose compatible with the new measurement.
Dryer hoses come in many different lengths. Non-flexible hoses cannot be altered in size. However, flexible, accordion hoses can be lengthened slightly, if necessary. If your hose is short by just a few inches, gently stretch the flexible hose pleats apart. This should give you the additional length you need. For non-flexible hoses, you can purchase an additional short length of hose, and connect it to the original hose with dryer vent clamps.