Best Outer Sleeves for LPs

Is there a recommended type of plastic sleeve to protect valuable record covers from aging, yellowing, etc? I can buy them very inexpensively from the Princeton Record Exchange, but wondered whether they would have the desired effect. I've also seen poypropylene sleeves sold online at Sleeve City. Any recommendations? Thanks very much!
i like the resealable japanese type. you don't slide the cover in and out of the sleeve each time you want to play an lp, so cover wear is kept to a minimum. they also do a pretty good job of sealing dust away from the cover and lp. ymmv, but I'd give them a shot.
I use the POLYPROPYLENE 12" sleeve with the 1-1/2" RESEAL Flap. Product number SPPLP1234R is 12-3/4 x 12-3/4, which is slightly loose on normal albums and just big enough for heavy gatefold lp's. Very reasonably priced if you buy 500 or more.
Bags Unlimited SLP3.
Keep in mind that the aging and yellowing of record jackets are a function of effects of light and humidity over time, not so much the absence of a plastic sleeve. The plastic sleeve principally serves to protect from wear (rubbing, scuffing, etc) and to keep out dust and other contaminants.

Sleeves with a foldover resealable flap will provide the best dust and contaminant protection, but the trade-off is a bit more trouble extracting and replacing the LP if one also actively plays the vinyl in one's collection.

I've found all of the current "crystal clear polypropylene" outer sleeves offered by Sleeve City to be excellent sleeves. For my purposes, I've come to prefer the "Ultimate" 2.5mm sleeves in both regular and box set sizes. Unlike other polypropylene sleeves sold elsewhere, these really seem to not cloud with age but do stay completely clear, giving a very nice appearance and allowing one to more easily read the spines of the records on the shelves.

Here's the link to the outer sleeves offered by Sleeve City: