Picked up a USMC bivvy for a reasonable price.  As advertised, the bug netting had unspecified damage/holes in it, but the rest of the bivvy seems new, possibly unused.

These items are not nearly as cheap as Army items; both for USMC cachet as well as being made in smaller numbers.

Initial impressions are that it's lighter than the typical surplus Army Bivvy, but likely also more fragile.  The insect netting over the "hood" of the USMC bivvy is a huge plus, compared to the Army unit, BUT being thin, fine mesh, easily damaged.  Tag inside the USMC bivvy cautions to use it over a sleeping pad or such to protect the bivvy against being perforated, and I thank that's a wise caution, bivvy being very thin.  USMC internal tag also mentions mesh storage bag, but not supplied.  Seems like a wise precaution as such would allow the bivvy to dry out a bit, if stored a bit damp.

Tag inside bivvy cover states: "One size fits all.", so the bivvy can be used with the Regular or Tall USMC sleeping bag; Tall sleeping bag being for 6' or over.

USMC bivvy has a zippered closure for the opening covered by the built-in insect netting; rolls down and is secured by a toggle closure. Zipper toggles for such are very small and suggest adding some suitable zipper-pulls to them.

There are some unexplained snapped loops inside the Bivvy.  Would appreciate info on these are for.

Having seen how the insect mesh is used in this bivvy, I'm wondering if some snap-attached sort of insect netting rig could possibly be attached to an Army bivvy.  With the DWR typically being applied to all Bivvys, suspect that sticky-back velcro is not viable alternative.  A person with a decent sewing-machine to sew-on velcro could dispense with snaps, I think.

For repair of the insect netting, suggest two possible approaches:

1) Use fine needle and fine, black, nylon thread (no shrinkage) to sew-shut small tears, perhaps the size of a dime or less.

2) For larger areas, suggest using This Item  Linked item is a "two-pack", and it is suggested to apply one patch inside the insect netting and a matching patch outside the netting.  If carefully applied, this patch sticks very well to clean netting.  Note that outside diameter of these patches is 3".  Other suitable patches of different sizes/dimensions might be available, so look around.

All I have for now; need to order some more patches to reinforce netting damage before I want to risk making existing netting damage worse.

Bottom Line:  Lighter than Army equivalent, but more fragile.  Has features that Army Bivvy lacks, but at a price in durability.

IMHO, USMC ought to have paid the extra $ in order to have the easily damaged insect net be a replaceable item instead of having it permanently attached.

As an aside, why the Army, USMC, USCG, and Air force "need" their own individual patterns of gear (and combat clothing) intended for the same purpose is beyond me.  I understand that certain items of gear are "mission specialized".  I get "Esprit de Corps".  But having entirely different bivvy sacks for the Army and Marines seems wasteful to me.

The much-detested Robert Strange McNamara was right on a few things.  IIRC, when he took office as SecDef, US military Branches required well over a dozen simple low-quarter shoes. Naturally he took it way to far, but he was right on the simple stuff.  Even a broken clock is right twice a day.

ETA: I have noticed a tendency of the applied patches, mentioned above, to "lift" from the netting after application.  Currently subjecting them to gentle solar heat, and firmly pressing the warmed adhesive into/onto the netting and the identical adhesive "backing" patch.  Possible some "added" (hairdryer) gentle heat will be required to "seat" the patches firmly, and without "lifting".   ETA: so far, solar input/heating has not been completely effective, and so moving on to "hairdryer" type of heat.  Will advise.

General info on marine sleeping system: https://www.trngcmd.marines.mil/Portals/207/Docs/FMTBE/Student%20Materials/FMSO%20Manual/105.pdf

USMC Sleeping Bag Initial Review: https://www.ar15.com/forums/armory/USMC-Bivvy-Sack-Initial-Review/10-535806/?page=1

The loops inside the USMC bivy are attaching points for the Coyote colored USMC sleeping bag.

Be advised there is a standard length size and a long size.

I have most every part of the USMC sleep system in Long - except the instruction card.

I really like this system.

I've used a glue gun to affix velcro strips to the bottom edge of a tarptent so I could add a skirt of mosquito netting around the circumference.  Might be a way to add a net to the Army bivvy?

Much obliged for helpful comments as to Long size vice Standard size USMC sleeping bags. I reckon most USMC sleeping bags were made--and sold as surplus--in Standard size.  IIRC, at least some of the Army MSS components are offered in Regular and Long sizes.

Glue gun glue is not at all flexible, so I doubt it suitable for this specific application--I could be wrong, though. Only way to find out is experimentation.

I'm not sure why the different patterns either, but I'd like to point out that MARPAT proceeds adoption of Scorpion... and UCP was an abomination

Thanks for the review,  I've been eyeing those both... but tbh,  I don't solo camp so it seems (for me) a waste of money.  Maybe once the kids are grown and move out, by which time I'll expect you to have reviewed this item's replacement

Interesting, some gives, some takes, but I think it will fit the bill for me.

Thanks for the review.

Got a "Long" USMC sleeping bag incoming.  Thanks for making this aspect clear.

There are some items of Army MSS system that are issued in "Long" sizes. For sure, the Army "Patrol Bag" is issued in "Long" size, and possibly other items.