Unfortunately, the product is not available and we no longer have that information on hand. We recommend reaching out to the manufacturer for this inquiry. Their contact information can be found here: https://slidefire.com/contact/
No, if you already have a mil-spec carbine buffer tube (with the adjustable positions), then you do not need the conversion kit.
The number of positions are determined by the buffer tube, not the stock. 4-position buffer tube? you have a 4-position stock. 6-position buffer tube? 6-position stock.
A movable cylinder or large pin in the stock drops into the matching receptacle in the buffer tube.
Of grater concern is whether your stock is mil-spec, or commercial. A commercial diameter stock is not compatible with this mil-spec buffer tube.
Mark H.
You would need to buy the stock as well to complete this conversion.