Slingshot Harness

by Number One Laboratories


The Slingshot Harness is made of strong elastic bands. It is designed specifically for use with Number One Laboratories STPs. This includes:

The Number One STP, The Sport STP, Model E STP

It may be possible to use this harness with other STPs and soft packers, however, we cannot guarantee that it will not damage your prosthetic. 


Use a measuring tape to measure the circumference around your thigh. Or use a ruler to measure the leg-hole in a pair of well-fitting briefs. 

XS: 14"-17" / 35cm-40cm

Small: 17"-20" / 40cm-50cm

Medium: 20"-24" / 50cm-60cm

Large: 24"-28" / 60cm-70cm

XL: 28"-32" / 70cm-80cm

Customer Reviews

Based on 13 reviews
andrew harris
pretty awesome

it’s very comfortable i ordered a size to big though i got an xl because that what i always get my underwear in but without my pants on it falls off my butt lol i still love it though

Great harness but a bit uncomfortable and chaffey.

The harness is great, fits snuggly against my body, but I've noticed that when I get up from sitting that I need to adjust the harness and stp a bit. Also, it's a bit uncomfortable when it rides up my butt and the straps get twisted, and the spandex chaffs when I sweat.

River Mars

the size chart isn’t really accurate. and for the price i would expect it to be a bit more comfortable. but overall a decent product. i definately have to shift around my stp quite a bit. it doesn’t really stay put.

Caiden Coleman
I love it

I had two orders delivery was long but i love everything

Angel Newsome

The slingshot works well but I’m excited to try the new one they just came out with that I bought!


Transguy Supply is a small 2 person team. You can generally expect your order to ship within 7-10 days of purchase.

Final Sales

Please note that due to the sensitive nature of the items in question, all STP, Packer, Harness, and Underwear sales are final. Please make sure you have double-checked product size guides and have selected the correct item.

International Orders

Please note that for all non-US orders, you may be charged local taxes in order to retrieve your order. See our Shipping Policies for more details.