The following information was provided to the Bloomington Stock Center by Trudi Schüpbach, Princeton University.
P{GAL4}GR1 (FBti0040373) is an insertion of P{GawB} on the third chromosome.  It drives expression in all follicle cells from early in oogenesis onward and may be used with UAS-FLP to make follicle cell clones.  It is probably not as strongly expressed in follicle stem cells as the second chromosome P{en2.4-GAL4}e22c insertion, because clones are usually somewhat smaller.
The expression of P{GawB}GR1 is described in Goentoro, L. A., Yakoby, N., Goodhouse, J., Schupbach, T., and Shvartsman, S. Y. (2006). Quantitative analysis of the GAL4/UAS system in Drosophila oogenesis. Genesis 44: 66-74 (FBrf0190676).