Well if the rubber cap that came on the tank counts then that would be it. However i don't consider that even close to this product.
Marker Setup:
Spyder pilot acs '05: 14" tru flight barrel
low rise clamping feed neck
dye sticky grips
run on HPA 72cc 3000psi
Strengths:
Stays on
Attaches well
Even when taken off still attached to the tank
Weaknesses:
Have to disassemble tank to attach cord
Review:
This type of product is a must need for any one that uses a nitro tank. Dirty or debris can severly damage your tank. $5 to $10 is a small amount to pay to ensure the safety of your tank. Ok I am done preaching....on to this product. This is as simple as any dust cover. Secures to the fill nipple tightly. Has a cord to attach to the tank so that even when filling you won't lose it. You do have to remove a burst disc or the gauge or even the fill nipple to attach the cord. Please if you don't know what you're doing take it to a pro shop.
Conclusion:
Over all solid product. A must have to protect your tank. Low price asorted colors. Really no reason to not have one.