The frame is constructed of long-fiber injection-molded plastics, making it extremely durable and resistant to chemicals and extreme hot and cold temperatures.
 The Pack Mule and Pack Rabbit frame systems are constructed of glass-filled injection molded nylon, which makes them extremely strong, lightweight, and flexible. They are designed to carry significant amounts of weight. However, like any product they can be damaged under the right conditions. In order to prevent damage to the frame, the best practice is to always strap your load back to the main frame. It is ok to place cargo on the cargo deck, but it should always be secured back to the main frame. Detailed Instructions.
The mounting position of the shoulder straps can be adjusted to correspond with the length of the user’s torso. The shoulder straps are held in place on the upper portion of the frame by interlocking straps, routed through the horizontal slots and secured either with Velcro or buckles. Reposition the straps to best accommodate the length of the user’s torso (measured from the lower back to shoulder). See Detailed Instructions. 
 Determining the right backpack size has no relation to height, but rather the length of the torso.  Torso length is used to determine the correct location of the XTreme Harness.  However, unlike traditional shoulder straps the XTreme Harness system requires slightly different placement.  The XTreme harness is intended to drape over the shoulders and not hang from the back of the neck.  If rubbing occurs along the back of the neck, the harness is attached too high on the frame.  Relocate the harness set to a lower position.  See Detailed Instructions here. 
First attach the Harness System to the frame. (Step 1.) Located at the apex between both shoulder straps are (2) 1” straps that are used to attach the harness to the frame.  Route the (2) 1” straps through the 1” slots located vertically along the top-center portion of the frame. (Step 2.) Weave the 1” straps through several slots and then return them back to the shoulder harness. (Step 3.) Weave each strap through the ladder lock and then back on itself, to create a secure non-slip attachment.(Step 4.) Detach the lower 1” straps of the shoulder harness from the tension lock. (Step 5.) Pass the looped ends through the 1” slots of the One-Piece Direct-Pull webbing (OPDP) attachment hardware. (Step 6.) Pass the running end through the looped end, pull tight, and reconnect the strap to the harness through the tension lock. Next attach the Hip Belt to the Frame. (Step 7.) Locate at the back end of each (left and right) sides of the hip belt are 1.5” straps.  These straps are used to attach the hip belt to the frame.  Route the (2) 1.5” straps through the 1.5” slots located on the One-Piece Direct-Pull webbing attachment hardware. (Step 8.) Pass the the running end through the 1.5” plastic hardware (ladder lock) sewn onto the hip belt. (Step 9.) Tighten the strap as needed to position the hip pad over the hip in a comfortable position. See Detailed Instructions here.
Click the following link to download the complete Assembly Instructions in pdf.
Located on the outside of the frame’s Tail sections are two mounting points that accommodate the Tensioners that provide resistance for the Lumbar suspension system. “Single” and “split” style Tensioners are interchangeable and provide for varying degrees of resistance. Mounting points located on the inside of each Tail section allow for the installation of additional Tensioners to provide further adjustment options.
Each Tensioner is kept in position by an Assembly Screw, which must be removed prior to making adjustments. In most cases each Tensioner can be removed by hand as long as there is no pressure applied to the Lumbar. (If needed, a flat-head screwdriver may be used to gently pry a tensioner off the mounting point.) When replacing a Tensioner onto a mounting point, be sure to position it behind the Bushing of the Connecting Rod, as this will provide the necessary resistance required for the Lumbar support. Lastly, replace the Assembly Screw to ensure that the Tensioner remains in position. Watch video.
While both frames are designed to exceed the rated weights, the large frame is rated for a maximum "seated-weight" of 250 lbs. (equals 330 lbs. total body weight) and the small frame is rated for a maximum "seated-weight" of 150 lbs. (equals 200 lbs. total body weight).
The original Pack Mule frame weighs 4.7 lbs., the new Pack Mule II frame weighs 4.1 lbs., and the Pack Rabbit frame weighs 1.9 lbs.
The PRP supplied shoulder straps are held in place on the upper portion of the frame by interlocking straps with Velcro or buckles and routed through the horizontal slots. The lower portion of the shoulder straps can be detached from the frame by removing the Threaded Knob that holds the 1-inch Webbing Connector in place. The “split-styled” configuration of the Webbing Connector is designed to rotate on and off the looped-end of the webbing without the need for cutting. Be sure to replace the Threaded Knob when complete.
The waistband can be detached from the frame by removing the Threaded Knob that holds the 1½-inch Webbing Connector in place. The “split-styled” configuration of the Webbing Connector is designed to rotate on and off the looped-end of the webbing without the need for cutting. Be sure to replace the Threaded Knob when complete. 
For ease of initial configuration, the Threaded Knobs of the Pack Mule frame are hand tight. Before use, it is recommended that both Threaded Knobs be tightened an additional 1/2 turn (maybe slightly more, if needed) beyond hand-tight to ensure that the lock washers are fully engaged. See Diagram. This can best be accomplished by applying simultaneous counter-torque using a set of pliers on each knob.  Recheck each knob periodically to ensure that it remains tight. 
Each Threaded Knob is held in place with a lock-washer. To release the Threaded Knobs from the lock-washers, each must be quickly and simultaneously turned counter-clockwise (opposite motions). This rapid movement should release both knobs and allow each to be unscrewed the remainder of the way. For best results: use a set of pliers on each knob to provide maximum grip and torque.
In some cases attaching another manufacturer’s pack to the frame is a simple plug-n-play process. In other cases a PRP Adapter Kit (sold separately) can be used to attach a commercially purchased pack to the frame. Please contact us for solutions tailored to specific packs. Watch video.
The Pack Rabbit (small) frame’s dimensions are H-13” x W-9” x D-8”, and accommodates torso lengths from 15.50-18.50" / 39.37-49.99cm. The Pack Mule (large) frame’s dimensions are H-22” x W-12” x D-9”, and accommodates torso lengths from 18.00-23.00" / 45.72-58.42cm. See more details.
The billing address MUST be the same as the address of the PayPal account or credit card used.  The shipping address can be any location to where the package will be sent.  The billing and shipping addresses DO NOT have to match.
International shipping is done through the United States Postal Service - International. Shipping costs vary by location. Depending on the country, a VAT (Value Added Tax) or Tariff may be required at the destination.  All Taxes, VAT, and Tariffs are the responsibility of the purchaser or importer. Read the Rules.
Pack Rabbit Products stands behind the quality of its products and we hope that you are happy with your gear. If you are unsatisfied for any reason, simply return your merchandise within 15 days of purchase, along with a brief explanation of the reason for the return. (Valid proof of purchase is required.) All returned items must be in new and unused condition. All returns must be shipped with a Return Authorization Number (RAN) noted. Please contact Customer Service to obtain an RAN. If possible, please return all merchandise in the original packaging. Please note: Final clearance items are not eligible for returns. Pack Rabbit Products will only honor returns of purchases made online at www.pack-rabbit.com. Products that are returned for exchange under warranty will be repaired if possible. If repair is not possible we will replace it. For products that are no longer in production you will be contacted by our Warranty Department to discuss replacement options. Questions about this policy can be directed to our Customer Service Department either at (214) 774-4363 or customerservice@pack-rabbit.com. Read the whole Policy
Please ship all returns/exchanged products to: PRP LLC., 4950 Westgrove Drive, Suite 130, Dallas, TX 75248. Please double check to ensure that you send your Return/Exchange to the correct address. Pack Rabbit Products is not responsible for returns lost in transit to our location. Read the whole Policy.
The customer is responsible to pay the Return/Exchange shipping charges. Products sent to the Warranty Department will be returned to the customer at the expense of Pack Rabbit Products. If expedited shipping is requested, any additional shipping charges will be billed to the customer. Read the whole Policy