Eureka Optima = Best Lightweight Bagless
The lightweight Eureka Optima bagless vacuum is one of the few vacuum cleaners in it's class with attachments. It is uncommon to see a vacuum hose an upright vacuum cleaner that weighs less than 12 pounds. The Eureka Optima hose is crush proof and give you the ability to adjust the suction.
The Eureka Optima is also different from other light vacuum cleaners because it it bagless. Bagless vacuums have been popular for years, but not in the lightweight category.
At least not anything that is remotely durable. You should probably be replacing your filter every 6 to 9 months if you are not washing it yourself, but no more trips to the store for vacuum bags. Neglecting the filters in this vacuum will cause problems.
The Optima is a very compact model vacuum, and store very well. The handle adjust to different heights. It's really an ideal size and weight for an apartment or a small home. This is not a heavy duty vacuum (non of the lightweight vacuums are), but it provides reasonable performance at a more than reasonable price.
You can be assured that the Eureka Optima is not made as well as a Simplicity or Riccar vacuum or for that matter an Oreck vacuum but the features of the Eureka Optima upright combined with the very low prices you can purchase it at make this vacuum cleaner a pretty decent buy. This vacuum is close to the price of one of those lightweight stick vacuums that you use to clean your kitchen or spot clean a rug in a busy restaurant, and your find find a lot of good deals on new and refurbished models.
Eureka Optima Vacuum Parts
If you own a Eureka Optima that looks like the model pictured above you will probably only need to be concerned with replacing filters. 
Most Eureka Optima light weight uprights use the Eureka 430 belt which is a geared belt that usually will last for the life of the vacuum. The Eureka Optima 430 series will usually use a DCF-10 or DCF-14 Eureka filters. The DCF-10 and the DCF-14 are the same exact size and some of the replacement filters will reflect that on the packaging. You may need to replace the roller in a few years but you will need to go to a vacuum shop or look online for that roller.
The Eureka Optima also differs from the higher quality light vacuum cleaners because it it bagless. Bagless vacuums have been popular for years, but not in the lightweight category. At least not anything that is remotely durable. You should probably be replacing your filter every 6 to 9 months if you are not washing it yourself, but no more trips to the store for vacuum bags. Neglecting the filters in this vacuum will cause problems.