According to the Spectek site this is 2.5v PC2100 DDR modules. The vendors website looks to be in error. Also this RAM has only a 1 year warranty. These modules look to be contract/spec units that are usually sold in large volumes to the big guys (Compaq, IBM, HP, etc.) for use in their products. Probably better grade than generics but not as good as Crucial. BTW, their site allows you to see if their product is recommended for use in your MB.