Sync inventory between product variants sold in different quantities. When a customer buys a pack of 6, stock for packs of 1, 3, and 12 updates automatically. Set a multiplier for each variant, pick a reference, and the app keeps everything in sync via webhooks. Scheduled sync is available for stores using 3PL or external fulfillment providers. Ideal for bundles, multipacks, and wholesale quantities. Works entirely within Shopify, no external services or accounts needed.