The usual choices are sand, glass or polymer beads, and light synthetic fills, and the right one depends on how much weight you want to carry. A Sling Steady bag ships filled with SteadyFill, a particulate polymeric fill, and you can add or remove it through hook-and-loop ports.
Lighter fill is easier to carry. Here is what makers publish.
Sand
Every maker states fill differently, so the figures below are as each maker or retailer lists them.
Sand is the traditional filler, and it is dense. Of the top PRS shooters surveyed by Precision Rifle Blog (11 October 2024), 67% used sand, about 17% light beads and 13% polymer beads.
WieBad lists its Mini Fortune Cookie at 7.8 lb filled with sand, as listed on 4 November 2026.
Glass and hybrid fills
The same WieBad bag is listed at 7.8 lb with glass and 6.2 lb with a hybrid fill, as listed on 4 November 2026.
Polymer beads and light fills
Polymer beads are the other common choice. Armageddon Gear's Game Changer is listed by one retailer (Altus Shooting, read 4 November 2026) at 7 lb with standard beads and 1.5 lb with SpexLite, a lightweight fill, and does not say whether those weights are filled or empty. Area 419 lists its RailChanger bag at 7 lb, with a fill weight of 5 lb standard or 3 lb light, and does not say whether the 7 lb is filled or empty.
Light fills are made for carrying. WieBad says its lightweight fill, listed at 1.0 lb in the Mini Fortune Cookie, gives up a little settle. MDT's Traveler is listed at 8 oz with Spex Lite or 1 lb with its house fill, and the page does not say whether those weights are filled or empty.
Can you choose how full the bag is?
Some makers let you. As listed on 4 November 2026, LS Wild offers a fill density of 2/3, standard or fully filled on its 2.5 Ultralight Rear Bag and Pack Pillow. Crosstac ships its bag overfilled with FlowFill LDPE media, zippered so the owner removes fill. TAB Gear's Cheater Bag ships with ultra-light fill and has a spout for the owner to fill it.
What weight does for you
A lighter bag is easier to carry. A bag on a bench is a different job from a bag carried up a ridge, and neither fill is right for every use.
If you carry the bag on the rifle all day, every ounce is on your shoulder.
Choosing by use
For a bench or a fixed position, a heavier fill is a fair choice. For a bag that stays on the rifle through a day in the field, a fill that is easy to carry matters more. If you do both, pick a bag whose fill you can change, so you can set the firmness for the day.
Filling a Sling Steady bag
Every Sling Steady bag is a rear shooting rest bag that sits under the stock, and it ships filled with SteadyFill. If it is firmer or softer than you want, hook-and-loop ports let you add or remove fill. Our post on setting bag firmness with SteadyFill walks through it.
In our testing, shots landed 28% closer to the bullseye with Sling Steady under the stock, and muzzle rise was about 75% lower. It also helps manage recoil.
The Pro 9", 9" x 2.5", is 9.5 oz, for bolt-action, sport and hunting rifles. The Sport 7", 7" x 2.5", is 6.3 oz in Black and 6.8 oz in other colors, for AR-platform rifles.
Where we sit
Some bags on the shelf weigh less than ours. As listed on 4 November 2026, MDT lists its Renegade Ultra-Light Shooting Bag at less than 2 oz, filled or empty not stated, and LS Wild lists its 2.5 Ultralight Rear Bag at about 2.5 oz in 500D Cordura. Both cost less than $89.99 too, at $79.99 and $65.00.
Sling Steady's case is a bag that stays on the rifle, with fill you can change. It rides on your sling or attaches directly. Made in the USA, $89.99. Sling Steady is a veteran-run company.
Both ship filled with SteadyFill: Pro 9" · Sport 7"
Related reading: Hard or soft: setting bag firmness with SteadyFill · What to look for in a lightweight rifle rear bag · What is a rear squeeze bag?
Sling Steady is Ready When You Are.