When you're looking through seals, gaskets, and o-rings, the real decision isn't just price-it's whether you need a part that drops into a specific assembly or a standard size you can use across multiple jobs. These two o-ring options sit at opposite ends of that trade-off. One is a matched pair for the piercing cap and valve on QB78-series air rifles; the other is a 25-piece lot of a common AS568-235 Buna-N o-ring for hydraulic, pneumatic, automotive, and general industrial sealing.
Quick verdict: If you own a QB78, QB78 Deluxe, XS78, or TH78 and need the factory-style piercing cap and valve seals, the QB78 Urethane set is the one to get. It's a direct fit at a lower price. If you need a standard AS568-235 o-ring in quantity for maintenance or repairs, the Buna 70 Duro set gives you 25 pieces to keep on hand.
| Product | Price | Quantity | Material | Price Bar |
|---|---|---|---|---|
| QB78 Piercing Cap & Valve O-Ring Seals | USD 5.75 | 2 | Urethane | |
| AS568-235 Buna 70 Duro O-Ring Set | USD 20.00 | 25 | Buna-N rubber |
Where Each Product Wins
QB78 Urethane O-Ring Seals wins if you need a precise replacement for the piercing cap or valve on a QB78-series air rifle. The two white urethane seals come with part numbers #3401 and #0409, and they're described as identical and interchangeable. At USD 5.75, it's a low-cost way to get exactly the right parts without buying a bulk assortment.
AS568-235 Buna 70 Duro O-Ring Set wins if you need a standard-size o-ring in volume. For USD 20.00, you get 25 pieces of Buna-N (nitrile) rubber with a 70 durometer hardness. That's a practical stash for hydraulic, pneumatic, automotive, fuel, or oil sealing jobs where a reliable, general-purpose o-ring is all you need.
Product Notes
QB78 Piercing Cap & Valve O-Ring Seals
These two white urethane seals are made for the piercing cap or valve on the QB78, QB78 Deluxe, XS78, and TH78, as well as other "78" variants. They're listed as #3401 and #0409, and the two are identical and interchangeable, so you have a spare or a matched pair depending on what you're repairing. Urethane gives them good strength, tear resistance, and abrasion resistance, which matters in a part that gets pressed and released repeatedly. At USD 5.75, this is an inexpensive, application-specific fix. The trade-off is that you only get two seals, and they're not intended for general o-ring duties-if you need a standard size for multiple machines, this won't cover that.
AS568-235 Buna 70 Duro O-Ring Set
This package of 25 AS568-235 Buna-N (nitrile) o-rings is a solid bulk choice for anyone who regularly works with standard-size seals. The 70 durometer hardness is a common middle-ground stiffness for hydraulic and pneumatic systems, and the description points to automotive, fuel, and oil sealing as typical uses. At USD 20.00, you're paying for quantity and versatility rather than a custom fit. It's new old stock, so the seals are unused but may have been sitting in inventory. The main limitation is that this is one specific size-AS568-235-and you need to confirm that matches your application before buying. It's not an assortment of different sizes, so it won't cover a wide range of repairs by itself.
Final Choice by Use Case
- For QB78 owners: The QB78 Piercing Cap & Valve O-Ring Seals are the obvious pick. They're exactly the right part, cost less, and include the two seals you need for that specific assembly.
- For general industrial or hydraulic work: The AS568-235 Buna 70 Duro O-Ring Set gives you 25 pieces of a widely used size, making it a better value if you have a known AS568-235 requirement.
- If you're unsure: Go with the QB78 set only if you're working on that air-rifle family. For everything else, verify your o-ring size and pick the bulk set that matches.
