Here's some industry info that may help you with your decision. The helical unit your looking at is being manufactured by one company. Though I never agreed with the practice of saturating the market and making it confusing for the consumer, the bare unit is sold to many 're-distributors' for them to re-box and label as they wish. When the source of the unit is 'dry', those distributors are the only ones that will have remaining stock until the entire market gets a new shipment from the source. The unit in question was designed and is being manufactured by Powertrax. Here's a link to the product...

https://www.powertrax.com/traction-systems-product/366744-limited-slip-differential-gt308730/?crt_viaSearch=partkeyword%3AGT308730

We currently have (1) unit left in stock. PM for price.