One material with different sizes

Hi.

We plan to produce many materials with different execution. For example one material can have 3 lenghts (L). For example

Material A, L=100

Material A, L=150

Material B, L=50

Material B, L=70.

So before producing I want to create reservation for Material A, L=100. How can I do it?

My ideas:

1. At first create batch for Material A with classification L=100 . And after that when create reservation put this butch. After that create production order and do goods receipt using this batch. But it is hard always create different batches for many materials with different classification.

2. Have 2 materials in SAP for material A:

Material C, L=100

Material D, L=150

In this case we do not create always batches. But have many Materials in the system.

So any advices?