These seals are high power seals for all Tx200's, SR, B40 and Pro Sport.
The Apex small seal has been used for years and ideal for the oversized tubes in many guns. The Tesla seal is for the older and newer guns with tight tubes that fall into the normal specification. Esp. Pro Sports. These are for higher velocity applications and as stated for the tight normal tubes. A parachute design to help adjust without fitting, but also designed for higher power. Perfectly fine in a FT gun as well. OD. .995" plus
Ideal for MK1-2-5 TX 200's, TX200 SRS. and especially the Pro Sport-All years.
On MK3 TX200- If your factory seal is way undersized- look at the Apex Small instead.
On New B40's-check what you need first. B26's are now in other countries taking the bigger Apex small seal.