Present a Bendix booster core in for pre paid rebuild and by mistake received a rebuilt Midland booster which requires a spacer. I installed w/o spacer and had some brake issues, but thought it was a caliper issue. At about 11 months booster failed and with the help of a WCC video realized I had the Midland booster and that I had ran it w/o spacer. Contacted Don and he had me send booster back for repair and immediately sent me a spacer. Within two weeks,I had booster back and mounted with correct spacer. Rebuild was warranted and additional parts were provided. Don took a difficult situation and turned it around quickly. Recommend WCC and it’s booster rebuild program.