Two Complete Kits, One Key Difference
When upgrading your AR15's stock and buffer system, you'll often see two types of kits: SOPMOD-style buttstocks and standard mil-spec buffer tube kits. Both provide the core components needed to replace or build a carbine-length stock setup, but they differ in stock profile, included parts, and intended use case.
We're comparing the ST004 AR15 SOPMOD Buttstock with Complete Mil Spec Buffer Tube Kit and the Star Tactical Supply AR-15 .223 5.56 MIL SPEC Butt Stock and Complete Mil Spec Buffer Tube Kit. Both kits include a stock body, mil-spec precision machined aluminum tube, spring, buffer, end plate, and castle nut. The main difference is the stock design: SOPMOD versus traditional mil-spec.
What Each Kit Includes
- ST004 AR15 SOPMOD Buttstock with Complete Mil Spec Buffer Tube Kits: Package includes: Stock Body, Mil-Spec Precision Machined Aluminum Tube, Spring, Buffer, End Plate & Castle Nut. Model: ST004. Confirms the ST004 kit is a complete drop-in replacement for a mil-spec buffer tube system, with the SOPMOD-style stock body as the distinguishing feature.
ST004 AR15 SOPMOD Buttstock with Complete Mil Spec Buffer Tube Kits - AR-15 .223 5.56 MIL SPEC BUTT STOCK AND COMPLETE MIL SPEC BUFFER TUBE KITS: This AR-15 .223 5.56 MIL SPEC butt stock and buffer tube kit from Star Tactical Supply includes the core components for a mil-spec stock setup. Includes stock body, mil-spec precision machined aluminum tube, spring and buffer, end plate and castle nut. Brand: Star Tactical Supply. Shows the Star Tactical kit is functionally identical in included parts, but uses a standard mil-spec stock body rather than a SOPMOD profile.
AR-15 .223 5.56 MIL SPEC BUTT STOCK AND COMPLETE MIL SPEC BUFFER TUBE KITS
SOPMOD vs Mil-Spec Stock Profile
The SOPMOD (Special Operations Peculiar Modification) buttstock is a collapsible carbine stock with a distinctive cheek rest that is slightly wider and more angular than a standard mil-spec stock. It often includes a storage compartment for batteries or small items. The ST004 kit uses this SOPMOD-style body, while the Star Tactical kit uses a conventional mil-spec buttstock.
Both stocks are designed to fit a mil-spec buffer tube. The supplied information confirms that both kits include a mil-spec precision machined aluminum tube, so the tube itself is the same standard diameter and length. The choice between them comes down to whether you prefer the ergonomics and storage of a SOPMOD stock or the simpler, lighter profile of a standard mil-spec stock.
Compatibility Considerations
Because both kits include a complete buffer tube assembly, they are drop-in replacements for any AR15 lower receiver that accepts a mil-spec buffer tube. No additional parts are needed beyond the kit itself. The supplied information does not specify the buffer weight or spring length, so if you have a specific barrel length or gas system, you may want to verify the buffer weight matches your setup. For most standard carbine-length gas systems, the included buffer should work fine.
Neither kit includes a stock wrench or installation tool, so you'll need a castle nut wrench and a punch for the end plate if you're replacing an existing stock. Both kits are offered only in a Standard option, with no color or finish variants listed.
ST004 SOPMOD Kit vs Star Tactical Mil-Spec Kit
- Stock Design: ST004 uses a SOPMOD-style buttstock with a wider cheek rest and storage compartment. Star Tactical uses a standard mil-spec collapsible stock.
- Included Parts: Both kits include stock body, mil-spec aluminum tube, spring, buffer, end plate, and castle nut. No additional parts required.
- Buffer Tube: Both use a mil-spec precision machined aluminum tube. Compatible with all mil-spec AR15 lower receivers.
- Price (catalog comparison): ST004 kit is listed at USD 27.44 (compare at USD 44.99). Star Tactical kit is USD 33.91 (compare at USD 52.99).
- Brand: ST004 is unbranded in the supplied info; Star Tactical kit is branded Star Tactical Supply.
Which Kit Should You Choose?
If you want the enhanced ergonomics and storage of a SOPMOD stock, the ST004 kit is the clear choice. It offers the same mil-spec tube and buffer components as the standard kit but with a more tactical stock profile. If you prefer a lighter, simpler stock or want a known brand, the Star Tactical kit is a solid option at a slightly higher price.
Both kits are functionally complete and will work in any mil-spec AR15 lower. The decision is purely about stock shape, brand preference, and budget. Neither kit includes installation tools or instructions, so plan accordingly.
